Clinical denouement and mutation analysis of patients with cystic fibrosis undergoing liver transplantation for biliary cirrhosis

Clinical denouement and mutation analysis of patients with cystic fibrosis undergoing liver transplantation for biliary cirrhosis

Clinical denouement and mutation analysis of patients with cystic fibrosis undergoing liver transplantation for biliary cirrhosis David R. Mack, MD, M...

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Clinical denouement and mutation analysis of patients with cystic fibrosis undergoing liver transplantation for biliary cirrhosis David R. Mack, MD, M o n i c a D. Traystman, PhD, John L. C o l o m b o , MD, Paul H. Sammut, MD, Stuart S. Kaufman, MD, Jon A. V a n d e r h o o f , MD, D e a n L. Antonson, MD, Rodney S. Markin, MD, PhD, Byers W. Shaw, Jr., MD, a n d Alan N. Langnas, DO From the Departments of Pediatrics, Pathology and Microbiology, and Surgery, University of Nebraska Medical Center, Omaha

Objective: To describe the clinical characteristics of patients with cystic fibrosis considered for liver transplantation and the clinical outcome after transplantation. Methods: Patient charts were reviewed. Mutation analysis was performed on blood or liver tissue samples with a panel of 17 mutations. Results:. Eight patients (five girls) with cystic fibrosis have undergone orthotopic liver transplantation for biliary cirrhosis. Mean age at transplantation was 12.0 years ± 7.7 years (range, 9 months to 23 years). Preoperatively, seven patients had mild to moderate pulmonary dysfunction and one moderate to severe pulmonary dysfunction. All patients required pancreatic enzyme replacement, and four patients required insulin for diabetes mellitus. The I -year survival rate was 75%, with no deaths related to septic events. Mean time of follow-up of the six operative survivors was 4.1 years ±1.9 years. Pulmonary function testing, in those serially tested, showed that forced expiratory volume in I second was maintained or improved and that forced vital capacity improved after transplantation. Mutation analysis showed the following genotypes: four patients, AF508/AF508;one patient, AF508/N 1303K; and three patients, ~F508/unknown. Conclusions: Despite the high risk of transplantation, these encouraging results indicate that liver transplantation should be considered for patients with cystic fibrosis and complications of end-stage liver disease. We could not demonstrate an unusual pattern of CF gene mutations in these patients with severe liver disease. it appeared that immunosuppressive agents did not have a deleterious effect on pulmonary function. (J PEDIATR1995;I 27:881-7) Cystic fibrosis is a systemic disease whose manifestations in the various organ systems are a consequence of mutations of a known gene] The localization of this protein to the apical plasma membrane of intrahepatic bile duct cells 2 may lead

Submitted for publication Feb. 10, 1995; accepted July 24, 1995. Reprint requests: David R. Mack, MD, Combined Section of Pediattic Gastroenterology and Nutrition, University of Nebraska Medical Center, 600 South 42nd St., Omaha, NB 68198-5160. Copyright © 1995 by Mosby-Year Book, Inc. 0022-3476/95/$5.00 + 0 9/20/68049

to abnormal ductular secretion and damage of the liver's functioning ability in a manner similar to that for other exocrine glands. 3 The liver injury in patients with CF is likely of an ongoing nature, and the increased longevity of survival among patients with CF may lead to increasing prevalence of advanced liver disease in these patients. 4, 5 Currently, therapy for complications from biliary cirrhosis remains difficult in patients with CF. Liver transplantation may offer a therapeutic option for the treatment of end-stage liver disease in these patients despite pulmonary colonization of microbial pathogens. 6-8 In this report we describe eight patients who

881

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See commentary, p. 944.

CF FEV1 FVC

Cystic fibrosis Forcedexpiratory volume in 1 second Forcedvital capacity

have undergone orthotopic liver transplantation for biliary cirrhosis. METHODS

Patients. Ten patients with CF were examined for liver transplantation between 1988 and 1994 at the University of Nebraska Medical Center, of whom eight (five girls) have undergone orthotopic liver transplantation. The two patients who were not considered for transplantation included one who had had only one episode of esophageal bleeding that was controlled by a single esophageal injection sclerotherapy session; the patient is currently well and has had no change in status. The other patient and family decided against any further consideration for transplantation during the evaluation process. All evaluations were performed as previously described. 9 Additional serologic studies revealed no abnormalities of copper, ceruloplasmin, or ferritin levels, or dysfunctional variants on protease inhibitor phenotyping. Direct bilirubin and aspartate aminotransferase measurements were performed on a Kodak Ektachem 750 analyzer (Johnson and Johnson Clinical Diagnostics, Rochester, N.Y.). Prothrombin time was determined with an MLA 1000 analyzer (Medical Laboratory Automation Inc., Coming, N.Y.). The mean age at the time of diagnosis of CF among patients was 2.3 +- 2.2 months (six had a diagnosis by 2 months of age and the other two at 5 months and 6 months of age). The mean age at the time of transplantation was 12.0 years +- 7.7 years -+7.7 years (range, 9 months to 23 years). Clinical and laboratory characteristics of patients at the time of evaluation are shown in Table I. Some of the standm'd hepatic blood tests are as noted, but there tended to be minimal elevations in their values. The exception was the youngest patient, who had required parenteral nutrition (as a consequence of short bowel syndrome) and had distal extrahepatic bile duct atresia, all of which may have contributed to deterioration of liver function. However, all patients had evidence of complications from portal hypertension. Splenomegaly was associated with thrombocytopenia (n = 8) and leukopenia (n = 6). Ascites had been noted in six patients, five of whom were successfully treated by the time of transplantation with combinations of diuretic agents and restriction of sodium and fluid intake. Bleeding from esophageal varices occurred in five patients. After esophageal sclerotherapy, there was recurrence in one patient and development of bleeding gastric varices in another two pa-

The Journal of Pediatrics December 1995

tients. Hepatic encephalopathy had developed in three patients, one of whom was requiring the continuous use of protein restriction and lactulose. The combination of these various factors led to the decision to offer liver transplantation. Orthotopic liver transplantation surgery was similar to that for non-CF patients, and biliary tree anastomoses were completed by both choledochocholedochostomy (n = 4) and Roux-en-Y choledochojejunostomy (n = 4). Associated findings, All patients were receiving pancreatic enzyme replacement therapy. Meconium ileus was diagnosed in infancy in two patients. Four patients were receiving insulin therapy for diabetes mellitus. Three of these patients were started on insulin therapy 2 months before transplantation. The condition of the fourth patient, who had been receiving insulin therapy 2 years before transplantation, was considered to be poorly controlled despite extensive efforts and good compliance; the patient was therefore considered for combined liver-pancreas transplantation. All eight patients had evidence of nutritional deprivation. Body measurements obtained in seven patients revealed a maximum triceps skin-fold measurement at the 30th percentile in two patients and less than the 5th percentile for age in the other patients. Similarly, mid-arm circumference determinations showed one patient at the 15th percentile and the remaining patients at or below the 5th percentile for age. Pulmonary evaluation. Seven of the eight patients had mild to moderate pulmonary dysfunction; the eighth patient had moderate to severe pulmonary dysfunction before transplantation, as determined by clinical examination and pulmonary function testing (two patients were too young for reliable testing) (Table II). Sputum samples were obtained for culture at the time of evaluation. Bacterial pathogens identified included Pseudomonas aeruginosa (5 patients), Staphylococcus aureus (2), Serratia marcescens (1) Xanthomonas maltophilia (1), and Morganella morganii (1). No patients had Burkholderia cepacia. Fungal pathogens observed included Aspergillus fumigatus (2) and Pseudallescheria boydii (1). One of the patients had allergic bronchopulmonary aspergillosis that was successfully resolved with corticosteroid therapy, but follow-up sputum examination revealed P. boydii. Before transplantation, all patients underwent vigorous physiotherapy, bronchodilator therapy, and antibiotic therapy. Intravenous amphotericin therapy was instituted for the patient with A.fumigatus who had no allergic manifestations. Spirometry was performed with a pneumotachometer spirometer (Cybermedic Inc., Boulder, Colo.) according to American Thoracic Society guidelines.l° The two youngest patients were not able to complete the testing preoperatively. Immunosuppression. Immunosuppressive agents employed consisted of cyclosporine and corticosteroids (one patient received tacrolimus and corticosteroids as part of a

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Mack et al.

883

Table I. Clinical characteristics of patients Pretransplantation laboratory evaluation Age (yr) at Patient transplanNo. Sex ration 1

M

9.25

2

F

3 4

Liverassociated symptoms

Direct Prothrombin AS'f bilirubin time (0-56 IJ/L) (-<5 IJmol/L) (10-13 sec)

Mutation analysis

Outcome Associated (time since conditions transplantation)

ev, gv, s, a, he

38

5

12.8

kF508/z~F508

PI

14.75

ev, gv, s, a

55

12

14.0

F F

8.7 22.9

ev, s, a ev, s, a

122 36

3.5 17

12.7 12.7

2~FS08/unknownPI, IDDM, He &FS08/zXF508 PI 2~F508/unknownPI, IDDM

5

F

13

ev, s, a, he

127

7

13.6

6 7

M F

5.17 0.75

ev, s s

160 418

7 133

13.6 12,2

8

M

21.58

s, a, he

108

18

14.6

Alive (5 yr I [ too) Dead (6 yr 2 too)

Alive (3 yr 9 mo) Alive (3 yr 1t mo) zkF508/N1303K PI, IDDM Dead (postoperatively) kF508/AF508 PI, MI Alive (4 yr 1 too) 2xF508/zXF508 PI, MI, PN, Dead (postDEI-IBA, operatively) IHE AF508/unknownPI, IDDM Alive (1 yr 4 mo)

ev, Esophageal varices; gv, gastric varices; s, splenomegaly;a, ascites; he, hepatic encephalopathy;AST, aspartate aminotransferase; PI, pancreatic insufficiency; IDDM, insulin-dependent diabetes mellitus; MI, meconium ileus; He, hemoptysis; DEHBA, distal extrahepatic biliary atresia; PN, parenteraI nutrition; IHE, in-

fantile hemangioendodielioma.

Table II. Pulmonary function testing before and after liver transplantation Patient No. l 2 3 4

6 8

After transplantation

Before transplantation Test

Evaluation

Proximate

FEVI FVC FEV1 FVC FEV~ FVC FEV1 FVC FEVa FVC FEV1 FVC

90* 85* 79* 76* 92 94 79* 91"

61" 68* 38* 50*

Proximate 75* 71" 72* 77* 79 83 67* 83*

At 6 mo

At I yr

At 2 yr

At 3 yr

At 4 yr

At >5 yr

107" 105"

114" I08" 114" 120" !03 105

ll0* 109" 101" 116" 105 105

114" 112" 106" i16" 105 108

105" i07" 71" 120"

118" 120"

76 81

91"

89 I22 45 68

44 68

46 82

43 80

All values are shown as percentage of the predicted value. *After bronchodilator therapy.

multicenter study) and were given as previously described.11 Whole blood cyclosporine and tacrolimus levels were obtained by the polyclonal method from Abbott Laboratories (Abbott Park, ILL). D N A analysis. Genomic D N A extraction, amplification, and analysis were performed as previously described.12 Genomic D N A was extracted either from whole blood preserved with ethylenediaminetetraacetic acid (five patients) or from preserved native liver tissue (three patients)] 3 The primer sequences and allele-specific oligomers used for mutation analysis have been reported previously. 12, 14, 15 The zXF508 mutation was analyzed with polyacrylamide gel

electrophoresis. Restriction endonuclease digestion was used to determine the presence of R334W, R347P/H, $549WN, G551D, R553X, R560T, 3849+10kbC-->T, G85E, and A455E mutations. Polymerase chain reaction and site-directed mutagenesis were used to analyze 62l + 1G-+T, N1303K, and 2~I507 mutations. Slot blot analysis was performed for the R l l 7 H , G542X, and W1282X mutations. Statistics. To assess the probability that the risk of diabetes mellitus requiring insulin in liver transplant recipients is different from that in the general CF population, we assumed percentages of CF in different age ~ o u p s with diabetes mellitus, reported by Fitz Simmons, 4 to be fixed and known.

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If the risk of diabetes among the eight patients studied was the same as for the general CF population, the number with diabetes mellitus treated with insulin would be approximately a Poisson random variable, with the mean X equal to 0.262. Comparison of the distribution of genotypes across categories was made by chi-squared test for contingency tables.

RESULTS Survival. One-year patient survival was 75 %. No patients died because of pulmonary complications or sepsis. There were two deaths related to early postoperative complications and unrelated to cystic fibrosis. One of the deaths was due to hepatic artery thrombosis and the other to primary aUograft nonfunction. Six patients survived the immediate postoperative period; mean survival time was 4.1 + 1.9 years. The one late death (>6 years after transplantation) was due to chronic renal failure in a patient who had refused further therapy. Pulmonary evaluations. As shown in Table II, five patients had pulmonary function testing performed before and six have had testing after liver transplantation. The studies done at the time of evaluation were at 2 months (three patients), 22 months, and 6 months before transplantation. Three patients had evidence of improvement after bronchodilator therapy and were considered to have asthma. Patients 1 and 2 had repeated spirometry studies just before transplantation because there was clinical deterioration in their pulmonary status, and one patient had uncontrolled ascites. All six surviving patients were able to have ventilator support discontinued on the first postoperative day. Serial spirometry determinations are shown in Table II (patient 4 has not had any further testing, and patient 6 was able to complete testing only 4 years postoperatively). Spirometry was first done 2 to 8 weeks after transplantation and showed similar percentages of predicted forced expiratory volume in 1 second and forced vital capacity, as found at the time of preoperative evaluation. Improvements in FVC were seen in all patients compared with their preoperative findings; good results were also found in patient 6. Similarly, FEV1 was maintained and in some cases improved in those in whom comparisons were possible; most of the improvement occurred in the first 6 to 12 months postoperatively. Long-term follow-up has show n deterioration only in patient 2, who had worsening renal function and poor compliance with therapy. Intravenous amphotericin therapy was given preoperatively to patients with A. fumigatus detected on sputum cultures, and one surviving patient also received aerosolized amphotericin postoperatively. Patient 8 was found postoperatively to have A. fumigatus on sputum cultures but had no evidence of pulmonary infection and was treated with oral

The Journal of Pediatrics December 1995

administration of itraconazole. Neither of the surviving patients acquired systemic or invasive pulmonary fungal infections. Four of the five patients with P. aeruginosa in sputum cultures preoperatively each had one pulmonary exacerbation related to this pathogen postoperatively. All patients improved within three weeks of therapy with chest physiotherapy, bronchodilator therapy and appropriate intravenous antibiotic therapy. The other patients did not have pulmonary exacerbations during the postoperative period. Mutational analysis. The most common CF mutation, AF508, was found in all patients from this group (12 of 16 chromosomes). Four patients were homozygous for the mutation (patients 1, 3, 6, 7). Of the four heterozygous patients, patient 5 was found to carry the additional mutation N1303K, but the remaining three patients did not carry mutations found in our panel and remain uncharacterized. To evaluate the distribution of mutations, we compared the chromosomal mutations of patients receiving liver transplantation with the mutations found among Nebraska patients with CF (minus the Nebraska patient who received a liver transplant)] ° and the North American patients with CF (minus Nebraska patients) at sites that tested the N1303K mutation. 16There was no significant difference in frequency of the AF508 mutation. Diabetes mellitus. Among these eight patients, four (Table I) required insulin for diabetes mellitus before liver transplantation. This rate is 15 times greater than that expected in the general population of patients with CF (p = 0.000008).

Other complications. Five patients have had a total of 10 episodes of acute allograft rejection; one patient had four rejection episodes. In this latter patient, it was difficult to maintain adequat e cyclosporine blood levels; treatment was therefore changed to tacrolimus. At 6 months after transplantation the remaining four patients required large doses of cyclosporine to maintain cyclosporine levels between 600 and 800 ng/ml. Three of the eight patients had grand mal seizures between 3 and 6 days postoperatively. Prodromal symptoms included headaches, disorientation, and irritability. There was no evidence of infectious causes, intracranial hemorrhages, hypoxic episodes, hypertensive crises, hypoglycemia, or electrolyte abnormalities. There were no differences between patients who had seizures and those who did not with respect to hypomagnesemia, cholesterol levels, or changes in cyclosporine levels. Histology. The recipient livers showed similar histologic features characterized by portal areas expanded by fibrosis with a mixed inflammatory infiltrate of lymphocytes, plasma cells, and some neutrophils. Prominent bile duct proliferation was present; original intralobular bile ducts were either

The Journal of Pediatrics Volume 127, Number 6

atrophic or distorted, and some contained intracellular lymphocytes, neutrophils, and luminal debris. Cholangioles were noted to contain inspissated bile (n = 4) and/or inspissated eosinophilic material (n = 2) in those regions evaluated. DISCUSSION Patients with CF have been increasingly considered for transplantation of lung, 1721 heart and lung, 17,22 pancreas,23 liver, 6s or combinations thereof. Deciding on candidates for lung transplantation has been influenced by studies of predictors of mortality rates for lung disease. 24 The same is not true for CF liver disease because of the low prevalence of severe biliary cirrhosis 4' 5 and the unique nature of CF liver disease. Standard liver function tests have not been useful in detecting the presence or progression of cirrhosis in most patients with CF 25, 26; thus the symptoms of portal hypertension may be the first indicator of significant liver disease. Consistent with the localization of the CF gene product in the liver to intrahepatic bile ducts, 2 prominent portal tract fibrosis with preserved hepatic architecture is characteristic. The significance of this abnormality, which is in contrast to other cirrhoses, is that portal hypertension and its sequelae, such as alimentary bleeding, can be prominent without marked hepatocellular failure. Deciding on an appropriate therapy for patients with portal hypertension and good hepatic functional reserve thus provides a dilemma in CF. Adding to the reservations regarding isolated liver transplantation have been the concerns about utilizing immunosuppressive agents in patients whose lungs are chronically colonized by microbial pathogens. Among our patients, no deaths were attributed to bacterial or fungal sepsis. This study adds to a growing body of experience indicating that the postoperative threat of pulmonary infections in patients with CF may not be any greater than in non-CF patients, and survival after liver Yansplantation compares favorably with survival after lung transplantation.17-19 Meiles et al.7 reported one death from Pseudomohas infection, and death from Aspergillus infection has been reported after liver transplantation in patients with CF. 6 Yet to be determined are the risks associated with isolated liver transplantation in patients with CF who have been colonized by B. cepacia. Serial spirometry detern-dnations showed continued improvement in FVC values and improvement in FEV1 in three of four patients tested; most of the improvement was recorded 6 to 12 months after transplantation. There has been no evidence of gradual deterioration among this small group of patients, as might be expected from previous longitudinal studies in which predicted FVC declined 2% to 3% each year, 27 except in one patient with poor compliance after transplantation. These findings are similar to those reported

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by Eigen et al.28 in subjects with CF who received prednisone for 24 to 48 months. The dose of prednisone in our patients was tapered, ll so they received much less than subjects of the Eigen study. In addition, liver transplant recipients received cyclosporine or tacrolimus. Other antiinflammatory agents have also been reported to slow the progression of lung disease. 29Taken together, this evidence indicates that medications that reduce the inflammatory response may positively affect the progression of CF lung disease. Malnourishment affecting respiratory muscle function 3° and pulmonary defense mechanisms, 31 splinting of the diaphragm by enlarged organs, edema, and hepatopulmonary syndrome 3234 may all contribute to pulmonary deterioration in patients awaiting liver transplantation and may account for the increased pulmonary mortality rate suspected in patients with both CF and liver disease. 5 The relief of many of these factors postoperatively may explain the improvement or maintenance of pulmonary function during the immediate period after liver transplantation, in comparison with sph'ometry values determined at the time of evaluation (Table H). Noble-Jamieson et al. s recently suggested that patients with CF and well-preserved lung function be considered for liver transplantation once varices are present. We would more likely attempt esophageal sclemtherapy if no other evidence of hepatic decompensation were present. Stringer et al) 5 reported on the safety and efficacy of injection sclerotherapy for the control of bleeding from esophageal vatices in patients with CF. Unfortunately, prevention of recurrent hemorrhage with the use of [3-blocking agents such as propranolo136 may be contraindicated in patients with CF because of their adverse effect of causing bronchoconstriction. Failure of esophageal sclerotherapy occurs in patients with CFY, 37 as in patients with other causes of portal hypertension, and sclerotherapy does not relieve all portal hypertension-associated problems. Other procedures to relieve the effects of portal hypertension besides transplantation have been performed 35, 37, 38 in patients with CF, the results of which are reported to be variable. 37, 39, 4o In addition, the underlying liver injury would not be expected to be static in nature, and we have not attempted these other procedures. There are several unique considerations for organ transplants in patients with CF, in comparison with other transplant recipients. Patients with CF have required large doses of cyclosporine 7, 8,17 because of their pancreatic insufficiency 41 and possibly because of increased drug clearance. 42 Increased dosages, more frequent dosing intervals, and administration of vitamin E to improve absorption 43 have been used. Impaired glucose tolerance is common in the general population of patients with CF, a4 but diabetes mellitus requiring treatment by insulin is not. 4 The incidence of diabetes mellitus was significantly greater in this series of pa-

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tients with severe liver disease than would be predicted. Whether this is related to impaired glucose metabolism or to altered insulin sensitivity remains to be determined. Nevertheless, patients with CF and treated diabetes mellitus have not been found to be different from patients without CF and without diabetes, with respect to survival, nutritional status, and pulmonary function.45 Liver transplantation can be performed safely in patients with diabetes,46 so these patients should not be excluded from liver transplant therapy. Insulin therapy improves lung function and reduces infections47 and current immunosuppressive agents alter glucose homeostasis, so evaluation and therapy for diabetes mellitus should be undertaken in all patients. Patients with CF and newly diagnosed, well-controlled diabetes may be expected to do well for many years with insulin therapy. 4s We conclude that liver transplantation should be considered for patients with CF and liver disease manifesting evidence of progressive hepatocellular decompensafion. Furthermore, immunosuppressive agents do not appear to have a deleterious effect on pulmonary function and may slow its rate of decline in patients with CF who are undergoing isolated liver transplantation. In those patients with esophageal variceal hemorrhaging without evidence of hepatic decompensation from biliary cirrhosis, injection sclerotherapy may offer benefit, but follow-up for failure of sclerotherapy and for determination of pulmonary function and general status is warranted so that liver transplantation can be considered. We are grateful for the assistance provided by Cheryl Calabro, BSN, for chart reviews, Greg Cochran,BS, MT(ASCP), and Elanor Zuvanich, BS, MT(ASCP), for their assistance in mutation analysis, and Dr. James Anderson for statistical analysis. REFERENCES

1. Rommens JM, Iannuzzi MC, Kerem B, et al. Identification of the cystic fibrosis gene: chromosome walking and jumping. Science 1989;245:1059-65. 2. Cohn JA, Strong TV, Picciotto MR, Naim AC, Collins FS, Fitz JG. Localization of the cystic fibrosis transmembrane conductance regulator in human bile duct epithelial cells. Gastroenterology 1993;105:1857-64. 3. Marino CR, Gorelick FS. Scientific advances in cystic fibrosis. Gastroenterology 1992;103:681-93. 4. FitzSimmons SC, The changing epidemiology of cystic fibrosis. J PEDIATR 1993;122:1-9. 5. Scott-JuppR, Lama M, Tanner MS. Prevalence of liver disease in cystic fibrosis. Arch Dis Child 1991;66:698-701. 6. Cox KL, Ward RE, Furginele TL, Cannon RA, Sanders KD, Kurland G. Orthotopic liver transplantation in patients with cystic fibrosis. Pediatrics 1987;80:571-4. 7. Mieles LA, Orenstein D, Teperman L, Podesta L, Koneru B, Starzl TE. Liver transplantation in cystic fibrosis [Letter]. Lancet 1989;1:1073.

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8. Noble-Jamieson G, Valente J, Barnes ND, et al. Liver transplantationfor hepatic cirrhosis in cystic fibrosis.Arch Dis Child 1994;71:349-52. 9. Shaw BW Jr, Wood RP, Kaufman SS, Williams L, Antonson DL, Vanderhoof J. Liver transplantation therapy for children. Part I. J Pediatr Gastroenterol Nutr 1988;7:157-66. 10. American Thoracic Society. ATS statement: Snowbird workshop on standardization of spirometry. Am Rev Respir Dis 1979;119:831-8. 11. Shaw BW Jr, Stratta RJ, Donovan J, Langnas AN, Wood RP, Markin RJ. Postoperativecare after liver transplantation.Semin Liver Dis 1989;9:202-30. 12. Traystman MD, Schulte NA, Colombo JL, et al. Mutation analysis and haplotype correlation for 139 cystic fibrosis patients from Nebraska Regional Cystic Fibrosis Center. Hum Mutat 1993;2:7-15. 13. Higuchi R. Rapid, efficient DNA extractionfor PCR from cells or blood. Amplifications 1989;2:1-3. 14. Friedman KJ, Highsmith WE Jr, Silverrnan LM. Detecting multiple cystic fibrosis mutations by polymerase chain reaction-mediated, site-directed mutagenesis. Clin Chem 1991;37:753-5. 15. Zielinski J, Rozmahel R, Bozon D, et al. Genomic DNA sequence of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Genomics 1991;10:214-28. 16. Cystic Fibrosis Genetic Analysis Consortium.Population variation among common CF mutations. Hum Mutat 1994;4:16777. 17. Starnes VA, Lewiston N, Theodore J, et al. Cystic fibrosis. Target population for lung lransplantationin North America in the 1990s. J Thorac Cardiovasc Surg 1992;103:1008-14. 18. Ramirez JC, Patterson GA, Winton TL, de Hoyos AL, Miller JD, Manrer JR. Bilateral lung transplantation for cystic fibrosis. J Thorac Cardiovase Surg 1992;103:287-94. 19. Metras D, Shennib H, Kreitmann B, et al. Double-lung transplantation in children: a report of 20 cases. Ann Thorac Surg 1993;55:352-7. 20. Noyes BE, Kurland G, Orenstein DM, Fricker FJ, Armitage JM. Experience with pediatric lung transplantation.J PEDIATR 1994;I24:261-8. 21. Spray TL, Mallory GB, Canter CB, Huddleston CB. Pediatric lung transplantation:indications, techniques, and early results. J Thorac Cardiovasc Surg 1994;107:990-1000. 22. Whitehead B, Helms P, Goodwin M, et al. Heart-lung transplantation for cystic fibrosis. II. Outcome. Arch Dis Child 1991;66:1022-6. 23. Stem RC, Meyes JT, Weber FL, Blades EW, Chulak JA. Restoration of exocrine pancreatic function following pancreasliver-kidney transplantation in a cystic fibrosis patient. Clin Transpl 1994;8:1-4. 24. Kerem E, Reisman J, Corey M, Canny GJ, Levison H. Prediction of mortality in patients with cystic fibrosis. N Engl J Med 1992;326:1187-91. 25. Colombo C, Battezzati PM, Podda M. Hepatobiliarydisease in cystic fibrosis. Semin Liver Dis 1994;14:259-69. 26. Williams SGJ, Westaby D, Tanner MS, Mowat AP. Liver and biliary problems in cystic fibrosis. Br Med Bull 1992;48:87792. 27. Corey M, Levison H, Crozier D. Five- to seven-year course of pulmonary function in cystic fibrosis. Am Rev Respir Dis 1976;114:1085-92.

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28. Eigen H, Rosenstein BJ, FitzSimmons S, Schidlow DV. A multicenter study of alternate-day prednisone therapy in patients with cystic fibrosis. J PEDIATR1995;126:515-23. 29. Konstan MW, Byard PJ, Hoppel CL, Davis PB. Effect of highdose ibuprofen in patients with cystic fibrosis. N Engl J Med 1995;332:848-54. 30. Coates AL, Boyce P, Muller D, Mearns M, Godfrey S. The role of nutritional status, airway obstruction, hypoxia, and abnormalities in serum lipid composition in limiting exercise tolerance in children with cystic fibrosis. Acta Paediatr Scand 1980;69:353-8. 31. James JW. Longitudinal study of the morbidity of diarrheal and respiratory infections in malnourished children. Am J Clin Nutr 1972;25:690-4. 32. Eriksson LS, Soderman C, Ericzon B-G, Eleborg L, Wahren J, Hedenstiema G. Normalization of ventilatior@erfusion relationships after liver transplantation in patients with decompensated cirrhosis: evidence for a hepatopulmonary syndrome. Hepatology 1990;12:1350-7. 33. Krowka MJ, Cortese DA. Hepatopulmonary syndrome: current concepts in diagnostic and therapeutic considerations. Chest 1994; 105:1528-37, 34. Barbe T, Losay J, Grimon G, et al. Pulmonary arteriovenous shunting in children with liver disease. J PEDIATR 1995; 126:5710. 35. Stringer MD, Price JF, Mowat AP, Howard ER. Liver cirrhosis in cystic fibrosis [Letter]. Arch Dis Child 1993;69:407. 36. Lebrec D, Poynard T, Hillon T, Benhamou J-P. Propranolol for prevention of recurrent gastrointestinal bleeding in patients with cirrhosis. N Engl J Med 1981;305:1371-4. 37. Feigelson J, Anagnostopoulos C, Poquet M, Pecau Y, Munck A, Navarro J. Liver cirrhosis in cystic fibrosis: therapeutic implications and long-term follow up. Arch Dis Child 1993; 68:653-7.

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38. Louis D, Chazalette J-P. Cystic fibrosis and portal hypertension interest of partial splenectomy. Eur J Pediatr Surg 1993;3: 22-4. 39. Stern RC, Stevens DP, Boat TF, Doershuk CF, Izant RJ, Matthews LW. Symptomatic hepatic disease in cystic fibrosis: incidence, course, and outcome of portal systemic shunting. Gastroenterology 1976;70:645-9. 40. Schuster SR, Shwachman H, Toym~a WM, Rubino A, TaikKhaw K. The management of portal hypertension in cystic fibrosis. J Pediatr Surg 1977;12:201-6. 41. Cooney GF, Fiel SB, Shaw LM, Cavarocchi NC. Cyclosporine bioavailability in heart-lung transplant candidates with cystic fibrosis. Transplantation 1990;49:821-3. 42. Mancel-Grosso V, Bertault-Peres P, Barthelemy A, Ch~alette JP, Durand A, Noirclerc M. Pharmacokinetics of cyclosporine A in bilateral lung transplantation candidates with cystic fibrosis. Transplant Proc 1990;22:1706-7. 43. Sokol RJ, Johnson ICE, Karrer FM, Narkewicz MR, Smith D, Kam I. Improvement of cyclosporin absorption in children after liver transplantation by means of water-soluble vitamin E. Lancet 1991;338:212-5. 44. Pfeifer T. Diabetes in cystic fibrosis. Clin Pediatr 1992;31: 682-7. 45. Reisman J, Corey M, Canny G, Levison H. Diabetes mellitus in patients with cystic fibrosis: effects on survival. Pediatrics 1990;86:374-7. 46. Trial KC, Stratta RJ, Larsen JL, et al. Orthotopic hepatic transplantation ha patients with type 1 diabetes mellitus. J Am Coll Surg 1994;178:337-42. 47. Lanng S, Thorsteinsson B, Nerup J, Koch C. Diabetes mellitus in cystic fibrosis: effect of insulin therapy on lung function and infections. Acta Paediatr 1994;83:849-53. 48. Sullivan MM, Denning CR. Diabetic microangiopathy in patients with cystic fibrosis. Pediatrics 1989;84:642-7.

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