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Sickle Cell Anemia
Sickle Cell Anemia JANE F. DESFORGES, M.D.* MAY Y. F. W. WANG, M.D.**
There is probably no disease with manifestations more diverse than sickle cell anemia. Because of this, it is of interest to all medical and surgical specialties and its complications may be in the province of any clinic or service. With the migration of large numbers of Negroes to northern cities in recent years, the problem of diagnosis and treatment of sickle cell disease has become frequent in many hospitals where, heretofore, it had been a rarity. Moreover, recent developments in the study of hemoglobinopathies, of which sickle hemoglobin is a model, have attracted the interest of both the practitioner and the basic scientist.
PATHOPHYSIOLOGY
Knowledge about the pathophysiology of the disease has gradually evolved. Approximately 50 years ago it was first observed that a patient with severe anemia had many sickle-shaped red corpuscles in his blood smear.17 It later became apparent that this defect resides in the red cell rather than in the plasma, and a number of investigators then showed that the degree of sickling can be controlled by the oxygenation of the blood. That an abnormality resides in the hemoglobin, itself, became clear with the work of Pauling and also with the observations of Harris. The former investigator documented for the first time that the sickle hemoglobin molecule has properties differing from the normal; with electrophoresis he demonstrated that it moves toward the anode at a slower speed than adult hemoglobin. 38 Soon thereafter, Harris was able to show that a solution of From The Tufts Hematology Laboratory, First and Third Medical Service, and The Pediatric Service of the Boston City Hospital, Boston, Massachusetts * Associate Professor of Medicine, Tufts University School of Medicine; Associate Director, Tufts Hematology Laboratory, Boston City Hospital ** United States Public Health Service Postdoctoral Fellow
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5 Pro
7 Glu
2 His
Figure 1. Hydrophobic bonding between the first amino acid valine and the substituted sixth amino acid, valine, of the beta chain of S hemoglobin. This allows hydrogen bonding between carbonyl of the first residue and NH of the fourth. (Reprinted from N ature34 through the kindness of M. Murayama with permission of the publishers.)
sickle hemoglobin under appropriate conditions of concentration and oxygen tension forms tactoids which under the microscope resemble the sickling of whole red blood cells. 14 Grossly, this is evident as increased viscosity or gel formation. At about this time Perutz described differences in solubility and crystalline structure of S hemoglobin. 41 The change in mobility in an electric field was later explained by the work of Ingram, who was able to pinpoint the defect to the substitution of a single amino acid in the beta chain of adult hemoglobin, in which glutamic acid is replaced by valine. 21 The amino acid replacement has a profound effect upon the intramolecular structure. Murayama has described a change in optical rotation when S hemoglobin forms a gel, reversal of S hemoglobin gelation at low temperatures, and the "melting" of S hemoglobin gel by propane, a hydrophobic molecule. BB • 34 On the basis of his findings, he has suggested that in each of the abnormal beta chains hydrophobic bonding occurs between the number 1 valine and the number 6 valine which has been substituted for
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glutamic acid. The resultant shift in molecular configuration allows for hydrogen bonding between the carbonyl group of valyll and the NH group of threonine, the fourth amino acid in this sequence (Fig. I). It is postulated that this intramolecular reorganization with change in shape allows for molecular "lock-and-key" interactions at complementary sites in the beta chain of one molecule and the alpha chain of the next. M This then leads to "stacking" of the hemoglobin molecules and the production of visible tactoids and of sickling of the red cell. Electron microscopic examinations of deoxygenated S hemoglobin reveals microtubules (Fig. 2, A). The dimensions of these microtubules suggest that, upon deoxygenation, six monofilament stacks of S hemoglobin molecules twist together to form a hollow molecular cable (Fig. 2, B).36 Oxygenation of the molecule may interfere with sickling by its effect of changing the distance between beta chains. 31 This could change the relationships so that the "key" of one chain is no longer available to the "lock" of the other. Sulfhydryl binding also inhibits sickling,l, 24 this presumably resulting from interference with SH-8H bonds and mercapto-mercapto interactions32 with resultant change in structure and loss of complementarity. Methemoglobin formation prevents sickling, probably also by a nonspecific mechanism of changing intramolecular relationships with loss of available complementary sites.
500 A
Figure 2. A, An electron micrograph of a microtubule of hemoglobin S. It appears to be hollow with an outer diameter of 170 A. (Reprinted from Science36 through the kindness of M. Murayama with permission of the publishers. Copyright 1966 by the American Association for the Advancement of Science.) B, A hollow cable formed by six strands of stacked molecules of hemoglobin S. (Reprinted from Science>6 through the kindness of M. Murayama with permission of the publishers. Copyright 1966 by the American Association for the Advancement of Science.)
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In a cell containing only S hemoglobin a mean corpuscular hemoglobin concentration of approximately 15 grams per 100 ml. of blood must be in the reduced form before sickling appears.l When S is combined with another hemoglobin, the total reduced hemoglobin necessary for sickling is greater than this.l, 44 In vivo, with an O2 tension of 40 mm. Hg and physiologic pH, about 45 per cent of the hemoglobin is deoxygenated; under these circumstances homozygous S cells would sickle, whereas "trait cells" would not, since the mean corpuscular hemoglobin concentration of reduced S hemoglobin plus reduced A hemoglobin would be insufficient for tactoid formation. Although no effect of pH between 6 and 8 has been demonstrated on the abnormal physical properties of sickle hemoglobin in hemolysates,l Greenberg et al. documented an adverse effect of low pH on intact red cells such that there is an increased tendency to sickling. l2 This is at least in part explained by the effect of low pH in favoring deoxygenation by a shift of the oxygen dissociation curve of hemoglobin. In heterozygous states, the accompanying hemoglobin is a factor in the degree of sickling. Less reduced S hemoglobin is necessary to produce a gel in an se than in an SA combination. 46 Fetal hemoglobin is in a sense protective and cells containing high F concentrations are most resistant to sickling. 46 It appears that A and do become a part of the tactoid structure, whereas F does not. l It is remarkable that this substitution of one amino acid in the hemoglobin molecule could have such far-reaching physiologic effects in the patient. These profound effects are due to the rigid deformity of the red cell caused by tactoid formation of its hemoglobin contents with resultant impaired blood flow in small vessels. In the patient with sickle cell disease the formation of a few sickle cells may lead to temporary obstruction of small vessels, resulting, in further anoxia, further sickling, and eventually in local metabolic acidosis Which will only enhance the sickling process. Thus, a vicious cycle is set Jp. The importance of flow is emphasized in a case report of tetralogy of Fallot and homozygous S disease by Pearson et al,39 They demonstrated a lack of close correlation between numbers of sickled cells and P0 2 in blood samples taken from various areas during cardiac catheterization. Moreover, the patient had more symptomatology due to sickle cell disease after surgical repair than before. The authors suggested that a rapid flow rate associated with a high output state prevented sickling from occurring maximally in areas of low P0 2 in this patient. If flow were rapid enough through an anoxic area, there might not be time for the physical change of sickling to take place. The time lag before production of sickling in in-vitro experiments is consistent with this hypothesis.
e
CLINICAL MANIFESTATIONS In sickle cell trait, when S is combined with A hemoglobin, there is always more adult hemoglobin produced than sickle. In such a case signs
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and symptoms seldom occur except with severe anoxia, as seen in high altitude flying in nonpressurized cabins. The site of predilection in such cases has been the spleen, and the findings have been left upper quadrant pain and tenderness, and frequent splenomegaly at times associated with a febrile response and leukocytosis. 7 Cyanotic heart disease may be a similar hazard in patients with sickle cell trait, and in one of our patients crises occurred as the heart disease worsened. There are certain areas of the circulation which are peculiarly prone to sickling because of the predominantly anoxic blood supply or because of the local variation in properties of the circulating blood. One of these areas is the kidney, where there is evidence of renal damage even in sickle cell trait. Such patients often are unable to concentrate urine. Perillie and Epstein have suggested that this is due to the local increase in tonicity of the blood supplying the renal tubules. 40 This increase in ionic concentration causes transient cellular dehydration and the resultant marked increase in the mean corpuscular hemoglobin concentration causes cells to sickle as they pass through the medullary circulation. Sickling here is also favored by a P02 somewhat lower than the P0 2 in venous blood elsewhere and a possible acid shift in pH. The concentrating defect is reversible in children but eventually the renal tubular cells suffer permanent damage in this process and irreversible hyposthenuria results. 25 The occasional occurrence of renal hemorrhage is probably related to the same pathophysiology with eventual infarct of renal medullary tissue. Pathologic studies of patients with what was probably sickle cell trait have revealed evidence of both tubular and glomerular involvement. 3o In homozygous S disease, along with extensive tubular damage, severe involvement of glomeruli may occasionally be seen.' There are also occasional reports of patients with sickle cell trait in whom thrombotic episodes in small vessels have been attributed to sickling. 26 ,36 These patients have suffered anoxia or necrosis of tissue, with symptoms localized to the area. Such cases are rare, but local abnormalities in flow or metabolism may make certain patients prone to this complication. In the newborn period when the predominant hemoglobin is fetal hemoglobin, sickle cell preparations may be negative even in a potential homozygous S.42 This is probably related to the small amount of S hemoglobin found in the neonate. It is only when fetal hemoglobin, which contains alpha and gamma chains, is replaced by the adult hemoglobin containing alpha and beta chains, that the sickle state Ca beta chain defect) becomes apparent. One seldom finds evidence of sickle cell disease even in a potential homozygote until after the first six weeks of life. After puberty, the natural course of the disease process appears to become somewhat attenuated, with decrease in the frequency of episodic crises. 23 The inheritance of other abnormal hemoglobins in association with S hemoglobin may lead to a varying degree of symptomatology. When S is accompanied by hereditary persistence of fetal hemoglobin, .. there is remarkably little symptomatology even though the concentration of S
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hemoglobin may be as high as 70 per cent. 6 This may be because hemoglobin :F does not appear to interact with S in the formation of tactoids.! On the other hand, when S is accompanied by C, the clinical features mimic those of homozygous S, although they tend to be somewhat milder. This would be consistent with the fact that C does interact with S in the formation of tactoids. 45 Moreover, the association of S hemoglobin with beta thalassemia may give a picture very similar to homozygous S disease. In both S-C and S thalassetnia, the proportion of S hemoglobin to the associated hemoglobin is greater than in S trait, leading to a tendency for intracellular tactoids at oxygen tension in ranges closer to physiologic. These patients do have one major difference from homozygous S. In the latter, the spleen enlarges in infancy as the disease appears, but during childhood it disappears, and in adult life only fibrotic remnants of the spleen remain. In contrast, splenomegaly persists throughout the course of the heterozygous disease states. Presence of splenomegaly, milder symptoms, milder anemia, and a large number of target cells on smears, all suggest S heterozygous with another abnormal hemoglobin. S hemoglobin may also occur in association with hemoglobins having alpha chain defects. Although such cases are uncommon, the pattern again seems to be that of milder disease. In order to classify the various sickle states, hemoglobin electrophoresis is necessary, and family studies are important. If heterozygosity with beta thalassemia is suspected, quantitative assay for fetal and A2 hemoglobins must be carried out. A clear distinction between homozygous S and heterozygous states cannot be made only from the clinical picture, nor do sickle cell preparations separate these conditions. There are certain aspects of the clinical state which bear special mention because of the frequency of symptomatology, the differential diagnoses, or the implications for treatment. One of these is the involvement of the cardiopulmonary system. Patients with sickle cell disease are prone to repeated episodes of acute pulmonary disease, the differential diagnosis of which often lies between pulmonary thrombosis and pneumonia. The patients may have chest pain, fever, cough productive of blood streaked sputum, clinical and x-ray evidence of parenchymal involvement, and leukocytosis. There is a good deal of evidence that thrombosis in situ may account for many of these episodes,29 and may be explained by the low mixed venous P02 and pH as well as the low flow through the pulmonary arterial circuit. Physiologic shunting of blood through unaerated pulmonary areas provides further sites for the beginnings of microthrombi, which can then propagate. Even if the lesion begins as an inflammatory one, the fever and the local depression of P0 2 and pH in an inflamed, unaerated area encourage formation of sickle cells and possible thrombosis. These repeated insults leave their mark on the pulmonary circulation and on the heart. Pulmonary hypertension and right ventricular hypertrophy may be seen in older patients, in whom cardiac function is already compromised by chronic anemia. Moser and Shea pointed out that the
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cardiac findings in sickle cell disease may be related in part to the cor pulmonale described above. 29 Such findings are difficult to distinguish from organic valvular disease and the differential diagnosis of rheumatic heart disease may be difficult. Another organ prone to damage is the liver. Impairment of hepatic function is commonly seen and is probably explained by sickling and sludging with resultant ischemia and necrosis induced in the low P0 2 environment of the portal circulation. Microscopic examination of the liver shows congestion of the sinusoids by sickle cells, engorgement of Kupffer cells with phagocytized erythrocytes and in some cases also necrosis of central parenchyma and bile plugs in the canaliculi. lo In one series, all patients over 16 years of age had elevated alkaline phosphatase and serum glutamic oxalacetic transaminase (SGOT).1 8 Occasionally, extreme jaundice may occur with elevation of both the direct and indirect bilirubin fractions and bilirubinuria. Since this may be associated with fever, leukocytosis, and abdominal pain, the differential diagnosis is often difficult, especially since chronic hemolysis may predispose to cholelithiasis. However, in 21 autopsies of cases of sickle cell disease, cholelithiasis was striking by its absence, being found in only one case of a 29 year old patient and even here there was no evidence of extrahepatic bile duct obstruction. ID Severe liver damage due to sickle cell disease with fatal termination in hepatic coma has been reported. 37 Figure 3 represents the course of a case with marked jaundice seen in our hospital. The patient was a 12 year old Negro boy with known homozygous S disease. He entered with the chief complaint of fever for 3 days and jaundice for 1 day. In addition to the findings illustrated in Figure 3, there was also marked guarding of 103
TEMPERATURE (OF)
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BILIRUBIN : : [ A : T O T A L (mg %)
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Figure 3. Course of patient with hyperbilirubinemic crisis. Note extreme degree of bilirubin elevation of both total and direct values.
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Figure 4. Anteroposterior roentgenogram of the hips shows marked irregularity of both femoral heads. There are cystic areas of bone destruction at the epiphyseal ends of each femur. Note the overall increase in bone density of all the pelvic bones as well as the shaft, neck, and head of each femur. The findings are characteristic of sickle cell disease with aseptic necrosis of the femoral heads. the abdomen, moderate tenderness in the right hypochondrium, and abdominal distention. A course of antibiotics was given without benefit. The abdominal pain and distention persisted for 6 days and then spontaneously subsided. Associated with the marked hyperbilirubinemia, SGOT was elevated to 130 units and bile was present in the urine. All these determinations returned to normal after 2 weeks. Oral cholecystogram obtained in the third week showed absence of stones and normal function. The skeleton is another system with multiple manifestation of sickle cell disease, and here again the problem is one of differentiating between infarction and infection. That these patients are prone to bone infarcts is best demonstrated by the frequency of aseptic necrosis of the head of the femur in sickle cell disease. Figure 4 represents an example of aseptic necrosis with associated bone changes. This patient had very little symptomatology related to this. Such an event may be heralded by severe pain or sometimes may occur without specific localizing signs or symptoms, except for the presence of a limp. Another striking clinical finding related to the skeletal system is the hand-foot syndrome. This syndrome is seen primarily in children with homozygous S in the first two years of life, and no instances have been seen over the age of seven years. 5 • 46 There is tense swelling and tenderness of the dorsum of the hands or feet, or both, accompanied by general irritability and fever for the average duration of one to two weeks. Leukocytosis may or may not be present. Roentgenographic examination at the time of onset
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of soft tissue swelling reveals no abnormality. The typical x-ray changes of periosteal new bone formation and radiolucent areas in several metacarpals, metatarsals, and/or phalanges usually occur in one to two weeks. The symptoms subside spontaneously and the x-ray changes eventually revert to normal. The most important differential diagnosis to be considered is osteomyelitis, which may rarely complicate the hand-foot syndrome.13 Sicklers have also been reported to have a high incidence of salmonella osteomyelitis ;20 it is possible that bone infarction may precede the localization of organisms at the site, which then becomes an area of osteomyelitis. In Figure 5 is an example of a child who had osteomyelitis of the ulna due to Salmonella typhimurium. Pregnancy may be associated with increased morbidity in patients with homozygous S27 and especially se disease. 8 In the latter, the disease may be completely quiescent until the third trimester of pregnancy, when rapid development of anemia, episodes of acute bone pain, or both, lead to the first specific diagnosis of a hemoglobinopathy. There have been several reports of maternal deaths occurring after only brief illness in the last trimester in se disease. Some of the deaths are due to pulmonary infarction,8 and yet postmortem examination may reveal nothing more specific than stasis of erythrocytes in various organs. 16 Homozygous S and se disease are also associated with increased incidence of spontaneous abortion, stillbirth, and prematurity.8, 27 It is possible that the low flow in the placental circulation with resultant placental infarcts is the cause of in-
Figure 5, An oblique roentgenogram of the forearm shows mottled destruction of the diaphysis of the ulna with associated irregular periosteal new bone formation. Findings are consistent with a diffuse osteomyelitis of the ulna.
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creased fetal wastage,2 but more definitive studies of placental pathology are needed. In the management of these cases, the consensus is to avoid interference with an already established pregnancy by such means as therapeutic abortion, early induction of labor, or cesarean section unless there are clear obstetric indications. 8 The use of transfusions and other therapy is determined by the symptomatology and degree of anemia. TREATMENT Treatment of crises depends upon the manifestations and their seriousness. Symptomatic relief for pain with analgesics may suffice but pain may be very severe and only partially relieved with such measures. For patients with severe and persistent' symptoms, other measures have been recommended. Scott and his colleagues have observed relief of symptoms by expanding plasma volume with dextran, fructose, and other fluids and have, in fact, observed an increase in circulating red cell mass with this treatment. 44 This is thought to be due to a flushing out of trapped sickle cells by these plasma volume expanders. Rapid infusion of large amounts of alkali has also been observed to relieve pain crises. l l This measure was first used because of the observation that alkali decreased in-vitro sickling. However, the amount required is large and the treatment may be complicated by electrolyte imbalance. Moreover, in view of Scott's reports, it is possible that the volume of fluid is more important as a therapeutic agent than the pH shift. Oxygen therapy may be of use in sickle crisis. Since the lungs are often not normal and the pulmonary circulation may be involved in the sickling crisis, this treatment may bring about an increase in O 2 content, and some clinical benefit thereby. Whether hyperbaric oxygen may play a role in crises is yet to be determined. Investigators at the Duke University Medical Center treated six patients with 100 per cent O 2 at 2 to 3 atmospheres for 30 to 60 minutes. Although there was a decrease in sickle forms in arterial blood samples, little beneficial clinical effect was apparent. One patient with a past history of convulsions had a convulsion at P0 2 of 1100 mm. 28 Since the symptoms are related to sludging and thrombosis, anticoagulants have also been considered for treatment and for prophylaxis in sicklers. However, this therapy has been complicated by hemorrhage and no clear-cut evidence of benefit has been demonstrated. 43 It is possible that underlying liver disease makes these patients prone to bleeding on such drugs. Moreover, since the mechanism of circulatory impairment is based on the rigid sickle cells rather than the actual formation of thrombus, hemorrhage at the site of infarction might occur in the presence of anticoagulants. A number of attempts have been made to alter the potential of the abnormal hemoglobin to sickle. One approach has been to induce chronic
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methemoglobinemia by methemoglobin-forming agents in order to limit the number of molecules available for tactoid formation. Although theoretically reasonable, however, this treatment was hampered by side effects and void of clinical benefit.4 Recently it has been suggested that phenothiazines may prolong the life span of the sickle cell in the circulation. 15 The degree of change reported, however, is not great and the clinical effectiveness of such drug treatment remains to be seen. There are certain general measures for prevention of crises which patients and their families may themselves recognize. Fatigue, exposure to cold, or stress may precipitate crises and these are to be avoided. It also appears that infections, fever, dehydration, and acidosis may induce a crisis. There are also crises associated primarily with anemia due either to increased hemolysis or marrow aplasia. There may be a sudden drop in hematocrit related to sequestration. This is especially common in homozygous S children who still have a palpable spleen. Although the process may be to some extent reversible, prolonged sequestration leads to destruction of these cells. Since such an episode may cause acute and profound anemia, parents should be advised to bring the child to the attention of a physician whenever there is a sudden change in his clinical state. Such a change can be extremely rapid and is the mechanism of sudden death occasionally seen in children with sickle cell disease. 22 In our experience, sudden death with severe anemia has occurred only in young children and it may be that the presence of the spleen plays a mortal role in this sequestration of sickled cells. At postmortem examinations, massive congestion of the spleen has been described in most cases of sudden death. 22 Anemic crises may also occur as a result of transient aplasia of the marrow. Such is occasionally seen with infections which are not themselves severe. It has been seen with mild viral illness, and can be a complication of any type of chronic hemolytic disease. Figure 6 illustrates the course of aplastic crisis seen in a three year old Negro girl with homozygous S. Bone marrow aspiration on the third hospital day revealed a hypo cellular marrow with myeloid :erythroid ratio of 96:1; the rare nucleated red cells seen were normoblastic. All bacterial cultures were negative. Mild otitis media and a relative lymphocytosis with several atypical lymphocytes suggested the presence of viral infection. More commonly, anemic crises are associated with a marrow which is malfunctioning because of a relative folate deficiency. In any type of myelo- or erythroproliferative disease, increased demands may outstrip a marginal dietary supply of this vitamin. 19 In the case of the sickler, demands of a constantly increased rate of erythropoiesis can be met with the supply of folate in an average diet; however, with a poor diet, a minor degree of malabsorption, or infection, megaloblastic changes occur. Pregnancy is, of course, a special problem in this regard, and such patients should receive a weekly supplement of 5 mg. of folic acid.
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Figure 6. Aplastic crisis in a case of sickle cell anemia associated with probable viral infection. Note virtual absence of reticulocytes for 7 days.
Consideration may also have to be given to prevention of disease in future generations. The pattern of inheritance of sickle hemoglobin is simple to explain. The possibilities of various combinations are spelled out in a Mendelian diagram and can be easily interpreted to the patients. It is probably fortunate that human eugenics has not achieved veterinary status, but it is also true that the patient may wish to have all the possibilities explained to him before he embarks on a reproductive venture. While the life span of the patient with sickle cell disease is not of normal length, with good medical care many survive to adulthood and are able to maintain an occupation and carry on a relatively normal, if somewhat limited, life. At this stage, the serious complications are related to lungs, heart, and liver. Complications related to therapy should be avoided by judicious care during early life. Transfusions are seldom needed and are only indicated with extreme anemia, and hemosiderosis should not be a problem. The patients should be advised to avoid phenacetin-containing drugs in view of the possible traumatic effect to the renal medulla when taken in large amounts. 9 They should also be discouraged from taking opiates for pain for obvious reasons. As in the treatment of all chronic disease, attention to family problems and the socioeconomic implications of the illness is vital to management of the patient. ACKNOWLEDGMENT
We are indebted to the Radiology Department of the Boston City Hospital for the films shown in Figures 4 and 5 and for their interpretation.
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REFERENCES 1. Allison, A. C.: Properties of sickle-cell hemoglobin. Biochem. J. 65: 212, 1957. 2. Apthorp, G. H., Measday, B., and Lehmann, H.: Pregnancy in sickle cell anemia. Lancet 1: 1344, 1963. 3. Bernstein, J., and Whitten, C. F.: A histologic appraisal of the kidney in sickle cell anemia. Arch. Path. 70: 407, 1960. 4. Beutler, E.: Effect of methemoglobin formation in sickle cell disease. J. Clin. Invest. 40: 1856, 1961. 5. Brooker, C. R., Scott, R. B., and Ferguson, A. D.: Studies in sickle cell anemia. XXII. Clinical manifestations of sickle cell anemia during the first two years of life. Clin. Pediat. 3:111, 1964. 6. Conley, C. L., Weatherall, D. J., Richardson, S. N., Shepherd, M. K., and Charache, C.: Hereditary persistence of fetal hemoglobin: A study of 79 affected persons in 15 Negro families in Baltimore. Blood 21: 261, 1963. 7. Conn, H. J.: Sickle cell trait associated with high altitude flying. New England J. Med. 251: 417, 1954. 8. Curtis, E. M.: Pregnancy in sickle cell anemia, sickle cell-hemoglobin C disease, and variants thereof. Am. J. Obst. & Gynec. 77: 1312, 1959. 9. Fifield, M. M.: Renal disease associated with prolonged use of acetophenetidincontaining compounds. New England J. Med. 269: 722, 1963. 10. Green, T. W., Conley, C. L., and Berthrong, M.: The Uver in sickle cell anemia. Bull. Johns Hopkins Hosp. 92: 99, 1953. 11. Greenberg, M. S., and Kass, E. H.: Studies on the destruction of red blood cells. XIII. Observations on the role of pH in the pathogenesis and treatment of painful crisis in sickle cell disease. Arch. Int. Med. 101: 355, 1958. 12. Greenberg, M. D., Kass, E. H., and Castle, W. B.: Studies on the destruction of red blood cells. XII. Factors influencing the role of S hemoglobin in the pathologic physiology of sickle cell anemia and related disorders. J. Clin. Invest. 36: 833, 1957. 13. Haggard, M. E., and Schneider, R. G.: Sickle cell anemia in the first two years of life. J. Pediat. 58: 785, 1961. 14. Harris, J. W.: Studies on the destruction of red blood cells. VIII. Molecular orientation in sickle cell hemoglobin solutions. Proc. Soc. Exper. BioI. & Med. 75: 197, 1950. 15. Hathorn, M., and Lewis, R. A.: Inhibition of sickling by phenothiazines. Effect on red cell survival. Brit. J. Haemat. 12: 195, 1966. 16. Henderson, A. B., Prince, A. E., and Greene, J. B.: Sickle cell disease variants and pregnancy. New England J. Med. 264: 1276, 1961. 17. Herrick, J. B.: Peculiar elongated and sickle-shaped red corpuscles in a case of severe anemia. Arch. Int. Med. 6: 517, 1910. 18. Hildovitz, G., and Jacobson, A.: Hepatic dysfunction and abnormalities of the serum proteins and serum enzymes in sickle cell anemia. J. Lab. & Clin. Med. 57: 856, 1961. 19. Hogan, J. A., Maniatis, A., and Moloney, W. C.: Serum folate clearance test in various hematologic disorders. Blood 24: 187, 1964. 20. Hook, E. W., Campbell, C. G., Weens, H. S., and Cooper, G. R.: Salmonella osteomyelitis in patients with sickle-cell anemia. New England J. Med. 257: 403, 1957. 21. Ingram, V. M.: Gene mutations in human haemoglobin: Chemical difference between normal and sickle-cell haemoglobin. Nature 180: 792, 1956. 22. Jenkins, M. E., Scott, R. B., and Baird, R. L.: Studies in sickle cell anemia. XVI. Sudden death during sickle cell anemia crises in young children. J. Pediat. 56: 30, 1960. 23. Kagwa, J., Ferguson, A. D., Scott, R. B., and Bullock, W. H.: Studies in sickle-cell anemia. XVIII. Clinical observations of prognosis and outlook beyond childhood. M. Ann. District Columbia 35: 1, 1966. 24. Kass, E. H., Ingbar, S. H., Harris, J. W., and Ley, A. B.: Chemical abnormalities in the erythrocytes in sickle cell anemia, their relationship to sulfhydryl metabolism and the effects of ACTH. J. Clin. Invest. 30: 652, 1951. 20. Keitel, H. G., Thompson, D., and Itano, H. A.: Hyposthenuria in sickle cell anemia: A reversible renal defect. J. Clin. Invest. 35: 998, 1956.
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26. Levin, W. C.: "Asymptomatic" sickle cell trait. Blood 13: 904, 1958. 27. McCurdy, P. R.: Abnormal hemoglobins and pregnancy. Am. J. Obst. & Gynec. 90: 891, 1964. 28. Mengel, C. E.: Personal communication. 29. Moser, K. M., and Shea, J. G.: Relationship between pulmonary infarction, cor pulmonale and the sickle states. Am. J. Med. 22: 561, 1957. 30. Mostofi, F. K., Vander Bruegge, C. F., and Diggs, L. W.: Lesions in kidneys in sickle cell disease. Arch. Path. 63: 336, 1957. 31. Muirhead, H., and Perutz, M. F.: Structure of hemoglobin. A three dimensional Fourier synthesis of reduced haemoglobin at 5.5. A resolution. Nature 199: 633, 1963. 32. Murayama, M.: On the nature of the interaction between binding sites for heavy metals (mercapto-mercapto interactions in normal human hemoglobin). J. BioI. Chem. 234: 3158, 1959. 33. Murayama, M.: A submolecular mechanism of gel formation in sickle cell haemolysate. Nature 194: 933, 1962. 34. Murayama, M.: A molecular mechanism of sickled erythrocyte formation. Nature 202: 258, 1964. 35. Murayama, M.: Molecular mechanism of red cell "sickling." Science 153: 145,1966. 36. Ob er, W. B., Bruno, M. S., Weinberg, S. B., Jones, F. M., and Weiner, L.: Fetal intravascular sickling in a patient with sickle-cell trait. New England J. Med. 263: 947, 1960. 37. Owen, D., Aldridge, J. E., and Thompson, R. B.: A fatal hepatic complication of sickle cell anemia. J. Mississippi M. A. 6: 107, 1965. 38. Pauling, L., Itano, H. A., Singer, S. J., and Wells, 1. C.: Sickle cell anemia, a molecular disease. Science 110: 543, 1949. 39. Pearson, H. A., Schiebler, G. L., Drovetz, J., Bartley, T. D., and David, J. K.: ; Sickle-cell anemia associated with tetralogy of Fallot. New England J. Med. I ~ 273: 1079, 1965. 40. Perillie, P. E., and Epstein, F. H.: Sickling phenomenon produced by hypertonic solutions: A possible explanation for the hyposthenuria of sicklemia. J. Clin. Invest. 42: 570, 1963. 41. Perutz, M. F., Liquori, A. M., and Eirich: X-ray and solubility studies of the haemoglobin of sickle-cell anemia patients. Nature 167: 929, 1951. 42. Porter, F. S., and Thurman, W. G.: Studies of sickle cell disease. Am. J. Dis. Child. 106: 35, 1963. 43. Salvaggio, J. E., Arnold, C. A., and Banov, C. H.: Long term anticoagulation in sickle cell disease. A clinical study. New England J. Med. 269: 182, 1963. 44. Scott, R. B.: Sickle cell disease. In Current Pediatric Therapy, 1965--1966. Philadelphia, W. B. Saunders Co. 45. Singer, K, and Singer, L.: Studies on abnormal hemoglobins. VIII. The gelling phenomenon of sickle-cell hemoglobin. Its biologic and diagnostic significance. Blood 8: 1008, 1953. 46. Watson, R. J., Burko, H., Megas, H., and Robinson, M.: The hand-foot syndrome in sickle cell disease in young children. Pediatrics 31: 975,1963. 818 Harrison Avenue Boston, Massachusetts 02118 (Dr. Desforges)
There is probably no disease with manifestations more diverse than sickle cell anemia. Because of this, it is of interest to all medical and surgical specialties and its complications may be in the province of any clinic or service. With the migration of large numbers of Negroes to northern cities in recent years, the problem of diagnosis and treatment of sickle cell disease has become frequent in many hospitals where, heretofore, it had been a rarity. Moreover, recent developments in the study of hemoglobinopathies, of which sickle hemoglobin is a model, have attracted the interest of both the practitioner and the basic scientist.
PATHOPHYSIOLOGY
Knowledge about the pathophysiology of the disease has gradually evolved. Approximately 50 years ago it was first observed that a patient with severe anemia had many sickle-shaped red corpuscles in his blood smear.17 It later became apparent that this defect resides in the red cell rather than in the plasma, and a number of investigators then showed that the degree of sickling can be controlled by the oxygenation of the blood. That an abnormality resides in the hemoglobin, itself, became clear with the work of Pauling and also with the observations of Harris. The former investigator documented for the first time that the sickle hemoglobin molecule has properties differing from the normal; with electrophoresis he demonstrated that it moves toward the anode at a slower speed than adult hemoglobin. 38 Soon thereafter, Harris was able to show that a solution of From The Tufts Hematology Laboratory, First and Third Medical Service, and The Pediatric Service of the Boston City Hospital, Boston, Massachusetts * Associate Professor of Medicine, Tufts University School of Medicine; Associate Director, Tufts Hematology Laboratory, Boston City Hospital ** United States Public Health Service Postdoctoral Fellow
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5 Pro
7 Glu
2 His
Figure 1. Hydrophobic bonding between the first amino acid valine and the substituted sixth amino acid, valine, of the beta chain of S hemoglobin. This allows hydrogen bonding between carbonyl of the first residue and NH of the fourth. (Reprinted from N ature34 through the kindness of M. Murayama with permission of the publishers.)
sickle hemoglobin under appropriate conditions of concentration and oxygen tension forms tactoids which under the microscope resemble the sickling of whole red blood cells. 14 Grossly, this is evident as increased viscosity or gel formation. At about this time Perutz described differences in solubility and crystalline structure of S hemoglobin. 41 The change in mobility in an electric field was later explained by the work of Ingram, who was able to pinpoint the defect to the substitution of a single amino acid in the beta chain of adult hemoglobin, in which glutamic acid is replaced by valine. 21 The amino acid replacement has a profound effect upon the intramolecular structure. Murayama has described a change in optical rotation when S hemoglobin forms a gel, reversal of S hemoglobin gelation at low temperatures, and the "melting" of S hemoglobin gel by propane, a hydrophobic molecule. BB • 34 On the basis of his findings, he has suggested that in each of the abnormal beta chains hydrophobic bonding occurs between the number 1 valine and the number 6 valine which has been substituted for
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glutamic acid. The resultant shift in molecular configuration allows for hydrogen bonding between the carbonyl group of valyll and the NH group of threonine, the fourth amino acid in this sequence (Fig. I). It is postulated that this intramolecular reorganization with change in shape allows for molecular "lock-and-key" interactions at complementary sites in the beta chain of one molecule and the alpha chain of the next. M This then leads to "stacking" of the hemoglobin molecules and the production of visible tactoids and of sickling of the red cell. Electron microscopic examinations of deoxygenated S hemoglobin reveals microtubules (Fig. 2, A). The dimensions of these microtubules suggest that, upon deoxygenation, six monofilament stacks of S hemoglobin molecules twist together to form a hollow molecular cable (Fig. 2, B).36 Oxygenation of the molecule may interfere with sickling by its effect of changing the distance between beta chains. 31 This could change the relationships so that the "key" of one chain is no longer available to the "lock" of the other. Sulfhydryl binding also inhibits sickling,l, 24 this presumably resulting from interference with SH-8H bonds and mercapto-mercapto interactions32 with resultant change in structure and loss of complementarity. Methemoglobin formation prevents sickling, probably also by a nonspecific mechanism of changing intramolecular relationships with loss of available complementary sites.
500 A
Figure 2. A, An electron micrograph of a microtubule of hemoglobin S. It appears to be hollow with an outer diameter of 170 A. (Reprinted from Science36 through the kindness of M. Murayama with permission of the publishers. Copyright 1966 by the American Association for the Advancement of Science.) B, A hollow cable formed by six strands of stacked molecules of hemoglobin S. (Reprinted from Science>6 through the kindness of M. Murayama with permission of the publishers. Copyright 1966 by the American Association for the Advancement of Science.)
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In a cell containing only S hemoglobin a mean corpuscular hemoglobin concentration of approximately 15 grams per 100 ml. of blood must be in the reduced form before sickling appears.l When S is combined with another hemoglobin, the total reduced hemoglobin necessary for sickling is greater than this.l, 44 In vivo, with an O2 tension of 40 mm. Hg and physiologic pH, about 45 per cent of the hemoglobin is deoxygenated; under these circumstances homozygous S cells would sickle, whereas "trait cells" would not, since the mean corpuscular hemoglobin concentration of reduced S hemoglobin plus reduced A hemoglobin would be insufficient for tactoid formation. Although no effect of pH between 6 and 8 has been demonstrated on the abnormal physical properties of sickle hemoglobin in hemolysates,l Greenberg et al. documented an adverse effect of low pH on intact red cells such that there is an increased tendency to sickling. l2 This is at least in part explained by the effect of low pH in favoring deoxygenation by a shift of the oxygen dissociation curve of hemoglobin. In heterozygous states, the accompanying hemoglobin is a factor in the degree of sickling. Less reduced S hemoglobin is necessary to produce a gel in an se than in an SA combination. 46 Fetal hemoglobin is in a sense protective and cells containing high F concentrations are most resistant to sickling. 46 It appears that A and do become a part of the tactoid structure, whereas F does not. l It is remarkable that this substitution of one amino acid in the hemoglobin molecule could have such far-reaching physiologic effects in the patient. These profound effects are due to the rigid deformity of the red cell caused by tactoid formation of its hemoglobin contents with resultant impaired blood flow in small vessels. In the patient with sickle cell disease the formation of a few sickle cells may lead to temporary obstruction of small vessels, resulting, in further anoxia, further sickling, and eventually in local metabolic acidosis Which will only enhance the sickling process. Thus, a vicious cycle is set Jp. The importance of flow is emphasized in a case report of tetralogy of Fallot and homozygous S disease by Pearson et al,39 They demonstrated a lack of close correlation between numbers of sickled cells and P0 2 in blood samples taken from various areas during cardiac catheterization. Moreover, the patient had more symptomatology due to sickle cell disease after surgical repair than before. The authors suggested that a rapid flow rate associated with a high output state prevented sickling from occurring maximally in areas of low P0 2 in this patient. If flow were rapid enough through an anoxic area, there might not be time for the physical change of sickling to take place. The time lag before production of sickling in in-vitro experiments is consistent with this hypothesis.
e
CLINICAL MANIFESTATIONS In sickle cell trait, when S is combined with A hemoglobin, there is always more adult hemoglobin produced than sickle. In such a case signs
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and symptoms seldom occur except with severe anoxia, as seen in high altitude flying in nonpressurized cabins. The site of predilection in such cases has been the spleen, and the findings have been left upper quadrant pain and tenderness, and frequent splenomegaly at times associated with a febrile response and leukocytosis. 7 Cyanotic heart disease may be a similar hazard in patients with sickle cell trait, and in one of our patients crises occurred as the heart disease worsened. There are certain areas of the circulation which are peculiarly prone to sickling because of the predominantly anoxic blood supply or because of the local variation in properties of the circulating blood. One of these areas is the kidney, where there is evidence of renal damage even in sickle cell trait. Such patients often are unable to concentrate urine. Perillie and Epstein have suggested that this is due to the local increase in tonicity of the blood supplying the renal tubules. 40 This increase in ionic concentration causes transient cellular dehydration and the resultant marked increase in the mean corpuscular hemoglobin concentration causes cells to sickle as they pass through the medullary circulation. Sickling here is also favored by a P02 somewhat lower than the P0 2 in venous blood elsewhere and a possible acid shift in pH. The concentrating defect is reversible in children but eventually the renal tubular cells suffer permanent damage in this process and irreversible hyposthenuria results. 25 The occasional occurrence of renal hemorrhage is probably related to the same pathophysiology with eventual infarct of renal medullary tissue. Pathologic studies of patients with what was probably sickle cell trait have revealed evidence of both tubular and glomerular involvement. 3o In homozygous S disease, along with extensive tubular damage, severe involvement of glomeruli may occasionally be seen.' There are also occasional reports of patients with sickle cell trait in whom thrombotic episodes in small vessels have been attributed to sickling. 26 ,36 These patients have suffered anoxia or necrosis of tissue, with symptoms localized to the area. Such cases are rare, but local abnormalities in flow or metabolism may make certain patients prone to this complication. In the newborn period when the predominant hemoglobin is fetal hemoglobin, sickle cell preparations may be negative even in a potential homozygous S.42 This is probably related to the small amount of S hemoglobin found in the neonate. It is only when fetal hemoglobin, which contains alpha and gamma chains, is replaced by the adult hemoglobin containing alpha and beta chains, that the sickle state Ca beta chain defect) becomes apparent. One seldom finds evidence of sickle cell disease even in a potential homozygote until after the first six weeks of life. After puberty, the natural course of the disease process appears to become somewhat attenuated, with decrease in the frequency of episodic crises. 23 The inheritance of other abnormal hemoglobins in association with S hemoglobin may lead to a varying degree of symptomatology. When S is accompanied by hereditary persistence of fetal hemoglobin, .. there is remarkably little symptomatology even though the concentration of S
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hemoglobin may be as high as 70 per cent. 6 This may be because hemoglobin :F does not appear to interact with S in the formation of tactoids.! On the other hand, when S is accompanied by C, the clinical features mimic those of homozygous S, although they tend to be somewhat milder. This would be consistent with the fact that C does interact with S in the formation of tactoids. 45 Moreover, the association of S hemoglobin with beta thalassemia may give a picture very similar to homozygous S disease. In both S-C and S thalassetnia, the proportion of S hemoglobin to the associated hemoglobin is greater than in S trait, leading to a tendency for intracellular tactoids at oxygen tension in ranges closer to physiologic. These patients do have one major difference from homozygous S. In the latter, the spleen enlarges in infancy as the disease appears, but during childhood it disappears, and in adult life only fibrotic remnants of the spleen remain. In contrast, splenomegaly persists throughout the course of the heterozygous disease states. Presence of splenomegaly, milder symptoms, milder anemia, and a large number of target cells on smears, all suggest S heterozygous with another abnormal hemoglobin. S hemoglobin may also occur in association with hemoglobins having alpha chain defects. Although such cases are uncommon, the pattern again seems to be that of milder disease. In order to classify the various sickle states, hemoglobin electrophoresis is necessary, and family studies are important. If heterozygosity with beta thalassemia is suspected, quantitative assay for fetal and A2 hemoglobins must be carried out. A clear distinction between homozygous S and heterozygous states cannot be made only from the clinical picture, nor do sickle cell preparations separate these conditions. There are certain aspects of the clinical state which bear special mention because of the frequency of symptomatology, the differential diagnoses, or the implications for treatment. One of these is the involvement of the cardiopulmonary system. Patients with sickle cell disease are prone to repeated episodes of acute pulmonary disease, the differential diagnosis of which often lies between pulmonary thrombosis and pneumonia. The patients may have chest pain, fever, cough productive of blood streaked sputum, clinical and x-ray evidence of parenchymal involvement, and leukocytosis. There is a good deal of evidence that thrombosis in situ may account for many of these episodes,29 and may be explained by the low mixed venous P02 and pH as well as the low flow through the pulmonary arterial circuit. Physiologic shunting of blood through unaerated pulmonary areas provides further sites for the beginnings of microthrombi, which can then propagate. Even if the lesion begins as an inflammatory one, the fever and the local depression of P0 2 and pH in an inflamed, unaerated area encourage formation of sickle cells and possible thrombosis. These repeated insults leave their mark on the pulmonary circulation and on the heart. Pulmonary hypertension and right ventricular hypertrophy may be seen in older patients, in whom cardiac function is already compromised by chronic anemia. Moser and Shea pointed out that the
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cardiac findings in sickle cell disease may be related in part to the cor pulmonale described above. 29 Such findings are difficult to distinguish from organic valvular disease and the differential diagnosis of rheumatic heart disease may be difficult. Another organ prone to damage is the liver. Impairment of hepatic function is commonly seen and is probably explained by sickling and sludging with resultant ischemia and necrosis induced in the low P0 2 environment of the portal circulation. Microscopic examination of the liver shows congestion of the sinusoids by sickle cells, engorgement of Kupffer cells with phagocytized erythrocytes and in some cases also necrosis of central parenchyma and bile plugs in the canaliculi. lo In one series, all patients over 16 years of age had elevated alkaline phosphatase and serum glutamic oxalacetic transaminase (SGOT).1 8 Occasionally, extreme jaundice may occur with elevation of both the direct and indirect bilirubin fractions and bilirubinuria. Since this may be associated with fever, leukocytosis, and abdominal pain, the differential diagnosis is often difficult, especially since chronic hemolysis may predispose to cholelithiasis. However, in 21 autopsies of cases of sickle cell disease, cholelithiasis was striking by its absence, being found in only one case of a 29 year old patient and even here there was no evidence of extrahepatic bile duct obstruction. ID Severe liver damage due to sickle cell disease with fatal termination in hepatic coma has been reported. 37 Figure 3 represents the course of a case with marked jaundice seen in our hospital. The patient was a 12 year old Negro boy with known homozygous S disease. He entered with the chief complaint of fever for 3 days and jaundice for 1 day. In addition to the findings illustrated in Figure 3, there was also marked guarding of 103
TEMPERATURE (OF)
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BILIRUBIN : : [ A : T O T A L (mg %)
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Figure 3. Course of patient with hyperbilirubinemic crisis. Note extreme degree of bilirubin elevation of both total and direct values.
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Figure 4. Anteroposterior roentgenogram of the hips shows marked irregularity of both femoral heads. There are cystic areas of bone destruction at the epiphyseal ends of each femur. Note the overall increase in bone density of all the pelvic bones as well as the shaft, neck, and head of each femur. The findings are characteristic of sickle cell disease with aseptic necrosis of the femoral heads. the abdomen, moderate tenderness in the right hypochondrium, and abdominal distention. A course of antibiotics was given without benefit. The abdominal pain and distention persisted for 6 days and then spontaneously subsided. Associated with the marked hyperbilirubinemia, SGOT was elevated to 130 units and bile was present in the urine. All these determinations returned to normal after 2 weeks. Oral cholecystogram obtained in the third week showed absence of stones and normal function. The skeleton is another system with multiple manifestation of sickle cell disease, and here again the problem is one of differentiating between infarction and infection. That these patients are prone to bone infarcts is best demonstrated by the frequency of aseptic necrosis of the head of the femur in sickle cell disease. Figure 4 represents an example of aseptic necrosis with associated bone changes. This patient had very little symptomatology related to this. Such an event may be heralded by severe pain or sometimes may occur without specific localizing signs or symptoms, except for the presence of a limp. Another striking clinical finding related to the skeletal system is the hand-foot syndrome. This syndrome is seen primarily in children with homozygous S in the first two years of life, and no instances have been seen over the age of seven years. 5 • 46 There is tense swelling and tenderness of the dorsum of the hands or feet, or both, accompanied by general irritability and fever for the average duration of one to two weeks. Leukocytosis may or may not be present. Roentgenographic examination at the time of onset
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of soft tissue swelling reveals no abnormality. The typical x-ray changes of periosteal new bone formation and radiolucent areas in several metacarpals, metatarsals, and/or phalanges usually occur in one to two weeks. The symptoms subside spontaneously and the x-ray changes eventually revert to normal. The most important differential diagnosis to be considered is osteomyelitis, which may rarely complicate the hand-foot syndrome.13 Sicklers have also been reported to have a high incidence of salmonella osteomyelitis ;20 it is possible that bone infarction may precede the localization of organisms at the site, which then becomes an area of osteomyelitis. In Figure 5 is an example of a child who had osteomyelitis of the ulna due to Salmonella typhimurium. Pregnancy may be associated with increased morbidity in patients with homozygous S27 and especially se disease. 8 In the latter, the disease may be completely quiescent until the third trimester of pregnancy, when rapid development of anemia, episodes of acute bone pain, or both, lead to the first specific diagnosis of a hemoglobinopathy. There have been several reports of maternal deaths occurring after only brief illness in the last trimester in se disease. Some of the deaths are due to pulmonary infarction,8 and yet postmortem examination may reveal nothing more specific than stasis of erythrocytes in various organs. 16 Homozygous S and se disease are also associated with increased incidence of spontaneous abortion, stillbirth, and prematurity.8, 27 It is possible that the low flow in the placental circulation with resultant placental infarcts is the cause of in-
Figure 5, An oblique roentgenogram of the forearm shows mottled destruction of the diaphysis of the ulna with associated irregular periosteal new bone formation. Findings are consistent with a diffuse osteomyelitis of the ulna.
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creased fetal wastage,2 but more definitive studies of placental pathology are needed. In the management of these cases, the consensus is to avoid interference with an already established pregnancy by such means as therapeutic abortion, early induction of labor, or cesarean section unless there are clear obstetric indications. 8 The use of transfusions and other therapy is determined by the symptomatology and degree of anemia. TREATMENT Treatment of crises depends upon the manifestations and their seriousness. Symptomatic relief for pain with analgesics may suffice but pain may be very severe and only partially relieved with such measures. For patients with severe and persistent' symptoms, other measures have been recommended. Scott and his colleagues have observed relief of symptoms by expanding plasma volume with dextran, fructose, and other fluids and have, in fact, observed an increase in circulating red cell mass with this treatment. 44 This is thought to be due to a flushing out of trapped sickle cells by these plasma volume expanders. Rapid infusion of large amounts of alkali has also been observed to relieve pain crises. l l This measure was first used because of the observation that alkali decreased in-vitro sickling. However, the amount required is large and the treatment may be complicated by electrolyte imbalance. Moreover, in view of Scott's reports, it is possible that the volume of fluid is more important as a therapeutic agent than the pH shift. Oxygen therapy may be of use in sickle crisis. Since the lungs are often not normal and the pulmonary circulation may be involved in the sickling crisis, this treatment may bring about an increase in O 2 content, and some clinical benefit thereby. Whether hyperbaric oxygen may play a role in crises is yet to be determined. Investigators at the Duke University Medical Center treated six patients with 100 per cent O 2 at 2 to 3 atmospheres for 30 to 60 minutes. Although there was a decrease in sickle forms in arterial blood samples, little beneficial clinical effect was apparent. One patient with a past history of convulsions had a convulsion at P0 2 of 1100 mm. 28 Since the symptoms are related to sludging and thrombosis, anticoagulants have also been considered for treatment and for prophylaxis in sicklers. However, this therapy has been complicated by hemorrhage and no clear-cut evidence of benefit has been demonstrated. 43 It is possible that underlying liver disease makes these patients prone to bleeding on such drugs. Moreover, since the mechanism of circulatory impairment is based on the rigid sickle cells rather than the actual formation of thrombus, hemorrhage at the site of infarction might occur in the presence of anticoagulants. A number of attempts have been made to alter the potential of the abnormal hemoglobin to sickle. One approach has been to induce chronic
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methemoglobinemia by methemoglobin-forming agents in order to limit the number of molecules available for tactoid formation. Although theoretically reasonable, however, this treatment was hampered by side effects and void of clinical benefit.4 Recently it has been suggested that phenothiazines may prolong the life span of the sickle cell in the circulation. 15 The degree of change reported, however, is not great and the clinical effectiveness of such drug treatment remains to be seen. There are certain general measures for prevention of crises which patients and their families may themselves recognize. Fatigue, exposure to cold, or stress may precipitate crises and these are to be avoided. It also appears that infections, fever, dehydration, and acidosis may induce a crisis. There are also crises associated primarily with anemia due either to increased hemolysis or marrow aplasia. There may be a sudden drop in hematocrit related to sequestration. This is especially common in homozygous S children who still have a palpable spleen. Although the process may be to some extent reversible, prolonged sequestration leads to destruction of these cells. Since such an episode may cause acute and profound anemia, parents should be advised to bring the child to the attention of a physician whenever there is a sudden change in his clinical state. Such a change can be extremely rapid and is the mechanism of sudden death occasionally seen in children with sickle cell disease. 22 In our experience, sudden death with severe anemia has occurred only in young children and it may be that the presence of the spleen plays a mortal role in this sequestration of sickled cells. At postmortem examinations, massive congestion of the spleen has been described in most cases of sudden death. 22 Anemic crises may also occur as a result of transient aplasia of the marrow. Such is occasionally seen with infections which are not themselves severe. It has been seen with mild viral illness, and can be a complication of any type of chronic hemolytic disease. Figure 6 illustrates the course of aplastic crisis seen in a three year old Negro girl with homozygous S. Bone marrow aspiration on the third hospital day revealed a hypo cellular marrow with myeloid :erythroid ratio of 96:1; the rare nucleated red cells seen were normoblastic. All bacterial cultures were negative. Mild otitis media and a relative lymphocytosis with several atypical lymphocytes suggested the presence of viral infection. More commonly, anemic crises are associated with a marrow which is malfunctioning because of a relative folate deficiency. In any type of myelo- or erythroproliferative disease, increased demands may outstrip a marginal dietary supply of this vitamin. 19 In the case of the sickler, demands of a constantly increased rate of erythropoiesis can be met with the supply of folate in an average diet; however, with a poor diet, a minor degree of malabsorption, or infection, megaloblastic changes occur. Pregnancy is, of course, a special problem in this regard, and such patients should receive a weekly supplement of 5 mg. of folic acid.
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Figure 6. Aplastic crisis in a case of sickle cell anemia associated with probable viral infection. Note virtual absence of reticulocytes for 7 days.
Consideration may also have to be given to prevention of disease in future generations. The pattern of inheritance of sickle hemoglobin is simple to explain. The possibilities of various combinations are spelled out in a Mendelian diagram and can be easily interpreted to the patients. It is probably fortunate that human eugenics has not achieved veterinary status, but it is also true that the patient may wish to have all the possibilities explained to him before he embarks on a reproductive venture. While the life span of the patient with sickle cell disease is not of normal length, with good medical care many survive to adulthood and are able to maintain an occupation and carry on a relatively normal, if somewhat limited, life. At this stage, the serious complications are related to lungs, heart, and liver. Complications related to therapy should be avoided by judicious care during early life. Transfusions are seldom needed and are only indicated with extreme anemia, and hemosiderosis should not be a problem. The patients should be advised to avoid phenacetin-containing drugs in view of the possible traumatic effect to the renal medulla when taken in large amounts. 9 They should also be discouraged from taking opiates for pain for obvious reasons. As in the treatment of all chronic disease, attention to family problems and the socioeconomic implications of the illness is vital to management of the patient. ACKNOWLEDGMENT
We are indebted to the Radiology Department of the Boston City Hospital for the films shown in Figures 4 and 5 and for their interpretation.
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REFERENCES 1. Allison, A. C.: Properties of sickle-cell hemoglobin. Biochem. J. 65: 212, 1957. 2. Apthorp, G. H., Measday, B., and Lehmann, H.: Pregnancy in sickle cell anemia. Lancet 1: 1344, 1963. 3. Bernstein, J., and Whitten, C. F.: A histologic appraisal of the kidney in sickle cell anemia. Arch. Path. 70: 407, 1960. 4. Beutler, E.: Effect of methemoglobin formation in sickle cell disease. J. Clin. Invest. 40: 1856, 1961. 5. Brooker, C. R., Scott, R. B., and Ferguson, A. D.: Studies in sickle cell anemia. XXII. Clinical manifestations of sickle cell anemia during the first two years of life. Clin. Pediat. 3:111, 1964. 6. Conley, C. L., Weatherall, D. J., Richardson, S. N., Shepherd, M. K., and Charache, C.: Hereditary persistence of fetal hemoglobin: A study of 79 affected persons in 15 Negro families in Baltimore. Blood 21: 261, 1963. 7. Conn, H. J.: Sickle cell trait associated with high altitude flying. New England J. Med. 251: 417, 1954. 8. Curtis, E. M.: Pregnancy in sickle cell anemia, sickle cell-hemoglobin C disease, and variants thereof. Am. J. Obst. & Gynec. 77: 1312, 1959. 9. Fifield, M. M.: Renal disease associated with prolonged use of acetophenetidincontaining compounds. New England J. Med. 269: 722, 1963. 10. Green, T. W., Conley, C. L., and Berthrong, M.: The Uver in sickle cell anemia. Bull. Johns Hopkins Hosp. 92: 99, 1953. 11. Greenberg, M. S., and Kass, E. H.: Studies on the destruction of red blood cells. XIII. Observations on the role of pH in the pathogenesis and treatment of painful crisis in sickle cell disease. Arch. Int. Med. 101: 355, 1958. 12. Greenberg, M. D., Kass, E. H., and Castle, W. B.: Studies on the destruction of red blood cells. XII. Factors influencing the role of S hemoglobin in the pathologic physiology of sickle cell anemia and related disorders. J. Clin. Invest. 36: 833, 1957. 13. Haggard, M. E., and Schneider, R. G.: Sickle cell anemia in the first two years of life. J. Pediat. 58: 785, 1961. 14. Harris, J. W.: Studies on the destruction of red blood cells. VIII. Molecular orientation in sickle cell hemoglobin solutions. Proc. Soc. Exper. BioI. & Med. 75: 197, 1950. 15. Hathorn, M., and Lewis, R. A.: Inhibition of sickling by phenothiazines. Effect on red cell survival. Brit. J. Haemat. 12: 195, 1966. 16. Henderson, A. B., Prince, A. E., and Greene, J. B.: Sickle cell disease variants and pregnancy. New England J. Med. 264: 1276, 1961. 17. Herrick, J. B.: Peculiar elongated and sickle-shaped red corpuscles in a case of severe anemia. Arch. Int. Med. 6: 517, 1910. 18. Hildovitz, G., and Jacobson, A.: Hepatic dysfunction and abnormalities of the serum proteins and serum enzymes in sickle cell anemia. J. Lab. & Clin. Med. 57: 856, 1961. 19. Hogan, J. A., Maniatis, A., and Moloney, W. C.: Serum folate clearance test in various hematologic disorders. Blood 24: 187, 1964. 20. Hook, E. W., Campbell, C. G., Weens, H. S., and Cooper, G. R.: Salmonella osteomyelitis in patients with sickle-cell anemia. New England J. Med. 257: 403, 1957. 21. Ingram, V. M.: Gene mutations in human haemoglobin: Chemical difference between normal and sickle-cell haemoglobin. Nature 180: 792, 1956. 22. Jenkins, M. E., Scott, R. B., and Baird, R. L.: Studies in sickle cell anemia. XVI. Sudden death during sickle cell anemia crises in young children. J. Pediat. 56: 30, 1960. 23. Kagwa, J., Ferguson, A. D., Scott, R. B., and Bullock, W. H.: Studies in sickle-cell anemia. XVIII. Clinical observations of prognosis and outlook beyond childhood. M. Ann. District Columbia 35: 1, 1966. 24. Kass, E. H., Ingbar, S. H., Harris, J. W., and Ley, A. B.: Chemical abnormalities in the erythrocytes in sickle cell anemia, their relationship to sulfhydryl metabolism and the effects of ACTH. J. Clin. Invest. 30: 652, 1951. 20. Keitel, H. G., Thompson, D., and Itano, H. A.: Hyposthenuria in sickle cell anemia: A reversible renal defect. J. Clin. Invest. 35: 998, 1956.
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26. Levin, W. C.: "Asymptomatic" sickle cell trait. Blood 13: 904, 1958. 27. McCurdy, P. R.: Abnormal hemoglobins and pregnancy. Am. J. Obst. & Gynec. 90: 891, 1964. 28. Mengel, C. E.: Personal communication. 29. Moser, K. M., and Shea, J. G.: Relationship between pulmonary infarction, cor pulmonale and the sickle states. Am. J. Med. 22: 561, 1957. 30. Mostofi, F. K., Vander Bruegge, C. F., and Diggs, L. W.: Lesions in kidneys in sickle cell disease. Arch. Path. 63: 336, 1957. 31. Muirhead, H., and Perutz, M. F.: Structure of hemoglobin. A three dimensional Fourier synthesis of reduced haemoglobin at 5.5. A resolution. Nature 199: 633, 1963. 32. Murayama, M.: On the nature of the interaction between binding sites for heavy metals (mercapto-mercapto interactions in normal human hemoglobin). J. BioI. Chem. 234: 3158, 1959. 33. Murayama, M.: A submolecular mechanism of gel formation in sickle cell haemolysate. Nature 194: 933, 1962. 34. Murayama, M.: A molecular mechanism of sickled erythrocyte formation. Nature 202: 258, 1964. 35. Murayama, M.: Molecular mechanism of red cell "sickling." Science 153: 145,1966. 36. Ob er, W. B., Bruno, M. S., Weinberg, S. B., Jones, F. M., and Weiner, L.: Fetal intravascular sickling in a patient with sickle-cell trait. New England J. Med. 263: 947, 1960. 37. Owen, D., Aldridge, J. E., and Thompson, R. B.: A fatal hepatic complication of sickle cell anemia. J. Mississippi M. A. 6: 107, 1965. 38. Pauling, L., Itano, H. A., Singer, S. J., and Wells, 1. C.: Sickle cell anemia, a molecular disease. Science 110: 543, 1949. 39. Pearson, H. A., Schiebler, G. L., Drovetz, J., Bartley, T. D., and David, J. K.: ; Sickle-cell anemia associated with tetralogy of Fallot. New England J. Med. I ~ 273: 1079, 1965. 40. Perillie, P. E., and Epstein, F. H.: Sickling phenomenon produced by hypertonic solutions: A possible explanation for the hyposthenuria of sicklemia. J. Clin. Invest. 42: 570, 1963. 41. Perutz, M. F., Liquori, A. M., and Eirich: X-ray and solubility studies of the haemoglobin of sickle-cell anemia patients. Nature 167: 929, 1951. 42. Porter, F. S., and Thurman, W. G.: Studies of sickle cell disease. Am. J. Dis. Child. 106: 35, 1963. 43. Salvaggio, J. E., Arnold, C. A., and Banov, C. H.: Long term anticoagulation in sickle cell disease. A clinical study. New England J. Med. 269: 182, 1963. 44. Scott, R. B.: Sickle cell disease. In Current Pediatric Therapy, 1965--1966. Philadelphia, W. B. Saunders Co. 45. Singer, K, and Singer, L.: Studies on abnormal hemoglobins. VIII. The gelling phenomenon of sickle-cell hemoglobin. Its biologic and diagnostic significance. Blood 8: 1008, 1953. 46. Watson, R. J., Burko, H., Megas, H., and Robinson, M.: The hand-foot syndrome in sickle cell disease in young children. Pediatrics 31: 975,1963. 818 Harrison Avenue Boston, Massachusetts 02118 (Dr. Desforges)