Osteogenesis imperfecta congenita

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Tile ] o u r n a t o/ P E D I A T R I C S

Osteogenesis imperfecta congenita Report

o f a case

Selected mesenchymat tissues were studied [rom a newborn in[ant with osteogenesis imper[ecta congenita. In addition to routine gross and microscopic examination o[ all organs, sections [rom skin, eyes, bones, and tendons were examined histochemically. Collagen was abnormal in the skin, cornea, and sclera and consisted o[ thin, haphazardly arranged, periodic acid-Sehiff positive argyrophitic fbers. The ossification o[ the skull was delayed. At the conversion line o[ the long bones, bare, calcified spicules o[ cartilage were seen. The underlaying bony spicules we,re covered by an abnormal, basophilie, P.A.S.-positive and argentophilic osteoid. The central core o[ calcified cartilaginous matrix persisted in the spongiosa spicules o[ the diaphysis. Nephrocalcinosis was an additional [eature noted.

Andrew Hreno, M.D., and M. Daria Haust, M.D. ~ KINGSTON~ ONT.~ CANADA

OSTEOGENESIS I~,~FECTA is a congenital and often hereditary systemic disorder of connective tissue, the manifestations of which can be extremely variable both in extent and severity. Considerable confusion existed in the early literature because of the variable manifestations of this disease, and the number of synonyms and eponyms 1 applied to this condition bear witness to this fact. Over the past several decades evidence has accumulated supporting the concept that the basic defect lies in the formation of tisFrom the Department o[ Pathology, Queen's University, and Kingston General Hospital, Kingston, Ont., Canada. "ZAddress~ Department o] Pathology, Richardson Laboratory, Queens University, K~ngston, Ont., Canada.

sues which are mesenchymal in origin and that the disorder can involve bone, skin, eyes, ligaments, tendons, fascia, teeth, and the inner ear. 1-6 Two varieties of this disorder are recognized: (1) a fetal or infantile type (osteogenesis imperfecta congenita) and (2) an adolescent or adult type (osteogenesis imperfecta tarda). The former is usually of such severity that the infant is often stillborn or dies in the early neonatal period, whereas in the latter the manifestations may be so mild that blue sclerae may be the only clinical feature present. Between the two extremes a wide spectrum of manifestation may exist, but in all cases the histopathology appears to be qualitatively similar. The purpose of this communication is to

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Fig. 1. External appearance of infant at autopsy showing symmetrical short~ ening and deformities of extremities. The limbs are tapered distally in a pseudomicromelic fashion. r e p o r t a case of osteogenesis i m p e r f e c t a c o n g e n i t a a n d to illustrate c e r t a i n m o r p h o logic a n d h i s t o c h e m i c a l f e a t u r e s w h i c h app e a r to be consistent w i t h the v i e w t h a t t h e basic d e f e c t involves tissues w h i c h are m e s e n c h y m a l in origin. CASE REPORT A white male infant was born at 34 weeks of gestation with a birth weight of 1,525 grams. The pregnancy was unremarkable and, following a short labor, the infant was delivered spontaneously with a breech presentation. The infant's cry immediately after birth was shrill and high pitched. T h e respirations became irregular and the infant died 30 minutes later despite resuscitative efforts. The parents, aside from being short in stature, were described as normal, as were the patient's 9 siblings. At autopsy the external features were typical of the fetal variety of osteogenesis imperfecta (Fig. 1). The head and the trunk were normal in size. There was marked symmetrical shortening and angulation of all four extremities which tapered distally. The skull was soft and pliable, and the sclerae were slightly blue. The testes were absent bilaterally from the scrotum. X-ray films (Fig. 2) revealed radiologic features compatible with the clinical diagnosis. There was generalized osteoporosis of the entire

Osteogenesis imper/ecta

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Fig. 2. Roentgenogram of infant showing multiple fractures in various stages of healing with secondary deformities in nmst of the bones. Many of the bones are osteoporotic. Beading of the ribs and clavicles is also seen. skeleton and multiple fractures in various stages of healing were present in all long bones with secondary angulation and shortening resulting in pseudomicromelia. T h e shafts of the long bones appeared to be somewhat widened. Irregular islands of ossification and extremely thin cortices were noted. The thoracic cage had a conical shape. Beading of the ribs was evident as a result of multiple healing fractures with callus formation. In addition, tee clavicles had a ribbonlike appearance. Unfortunately the vault of the skull was poorly visualized so that the mosaic pattern of Wormian bones frequently present in this disorder was not demonstrated. The examination of the internal organs was unremarkable except for the presence of fetal atelectasis and a subdural and subarachnoid hemorrhage in the occipital fossa. These findings were considered to be the immediate cause of the infant's death. Special attention was directed to the histology and histochemistry of the skin, eyes, skeletal system, tendons, and pulmonary vessels. Tissues removed from a fetus of comparable weight (1,540 grams) served as controls. All tissues were fixed in Muller's solution, ~" embedded in paraffin, cut, and stained with hematoxylin and eosin; hemalum-phloxine-saffron; Masson's tri"X'Muller's solution contains: potassium dichromate, 90 parts; 40 per cent formal, 10 parts.

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Fig. 4. Skin of control. Epidermal thickness is equal to that in Fig. 3. Corium is thick and dense with collagen bundles arranged in a parallel fashion. Skin appendages are well contained within the corium. Stain and magnification as in Fig. 3. Fig. 3. Skin of patient, Corium is reduced in thickness and has a loose spongy appearance. Skin appendages extend below corium into underlying subcutaneous fat. (Hemalum-phloxin-saffron stain. Original magnification x36.)

Fig. 6. Detail of corium of control. Corium is composed of thick mature collagen fibres (dark gray in photograph, brown in section). Stain and magnification as in Fig. 5. Fig. 5. Detail of corium of patient. Corium is composed of fine delicate argyrophilic fibres (black in photograph, black in section) which form a loose spongy network. (Gomori silver stain. Original magnification x972.) chrome; Weigert-Hart-metanil yellow-nuclear fast red; and the periodic acid-Schiff (P.A.S.). In addition the Gomori's silver impregnation was carried out on tissues fixed in formalin and sections of kidneys were stained with von Kossa's stain for calcium. Sections of the skin (Fig. 3) revealed a normal epidermis but the corium was thin and had a loose appearance. The skin appendages extended through the corium into the underlying fat. In the skin of the control infant (Fig. 4) the appendages were well contained within the dense corium. U n d e r higher magnification (Fig. 5) the individual fibers of the abnormal corium were thin, delicate, and lacy and appeared to form a loose spongy network, whereas in the control skin (Fig. 6) the mature thick collagen bundles had a parallel arrangement. Many of these thin fibers which were particularly abundant in the immediate subepithelial layer gave a positive reaction with silver impregnation (Fig. 5) and with P.A.S. stain, and they were light blue in Masson's

trichrome. In the skin of the control infant (Fig. 6) the argyrophilic and P.A.S.-positive fibers were relatively rare. With elastica stain, no abnormalities of elastic tissues were seen. Features comparable to those seen in the skin were also found in the eyes. The cornea (Fig. 7) and the sclera (Fig. 9) of the eye under study were appreciably thinner than those of the control eyes (Figs. 8 and 10), and many of the delicate component fibers were found to be argyrophilic and P.A.S. positive. Examination of the tendons revealed no abnormal features. Sections of the skull (Fig. 11) showed features comparable to those of a 3- to 4-month-old embryo. Small isolated islands of membranous bone were surrounded by a young immature type of fibrous stroma. Ossification was normal and a continuous plate of compact bone was present in the control skull (Fig. 12). In the epiphyses of the long bones and ribs, growth, maturation, and degeneration of the in-

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Osteogenesls imperfecta

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Fig. 8. Cornea of control. Thickness of cornea is greater than that in Fig. 7. Stain and magnification as in Fig. 7. Fig. 7. Cornea of patient. Cornea is reduced in thickness. (Hemalum-phloxlnesaffron stain. Original magnification x36.)

Fig. 10. Sclera of control. Fibrous coat is thicker than that in Fig. 9. Stain and magnification as in Fig. 9. Fig. 9. Sclera of patient. Fibrous coat is thinner than that in control (Fig. 10). (Hemalum-phloxine-saffron stain, Original magnification x36.)

Fig. 12. Skull of control. A continuous plate of compact bone, perforated by vascular spaces is present. Stain and magnification as in Fig. 11. Fig. 11. Skull of patient. Small isolated islands of membraneous bone (A) are present and are surrounded by a young fibrous stroma (B). (Hemalum-phloxine-saffron stain. Original magnification x27.)

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dividual cartilage cells were normal. At the conversion line level, however, certain features of endochondraI ossification differed from the normal process (Fig. I3). Calcified spicules of cartilage entirely bare of either osteoid or bone formed a prominent lattice, whereas in the control bone (Fig. 14) the spicules were covered by the usual complement of osteoid. In addition, many microfractures of these spicules were present in this layer. I n the areas below the conversion line many of the spicules of calcified cartilage were found to be covered by a layer of material resembling osteoid but possessing different staining properties. In hematoxylin and eosin stain this material was found to be basophilic (Fig. 15), whereas the normal osteoid of the control was acidophilic. T h a t this material differed from the usual osteoid was further demonstrated by its intense P.A.S. reaction (Fig. 16) and its strong argyrophilia. P.A.S. positivity and argyrophilia of the control osteoid was considerably less intense. Certain cellular elements in the area of endochondral ossification

also appeared to be abnormal. Instead Of the typical, plump, deeply basophilic osteoblasts, spindle-shaped cells with rather pale basophilic cytoplasm were present both in the stroma of the spongiosa and within the atypical osteoid (Figs. 13, 15, and i6). Although multinucleated osteoclasts were also present, these were relatively rare as compared to that of the control. In the diaphysis, the spicules of the spongiosa were thin and delicate. A persistent central core of calcified matrix of cartilage was present in most of these, whereas in the control the spicules were composed entirely of lamellar bone. At the site of fractures repair appeared to be proceeding normally, and in these areas large subperiosteal islands of cartilage formed an integral part of the callus. The cortex was extremely thin, and occasionally the cortical bone was almost entirely absent. The periosteum, particularly the fibrous layer, was also reduced in thickness so that the cambium layer appeared to be relatively thicker than normal. Sections of the kidneys showed a certain de-

Fig. 13. Spicules at conversion line of femur of patient. Spicules of calcified cartilage matrix are completely bare of either osteoid or bone. Note atypical spindle-shaped osteoblasts. (Hernalumphloxine-Saffron stain. Originat magnification x244.)

Fig. 14. Spicules at conversion line of femur of control. Spicules of calcified cartilage matrix are covered by osteoid (dark gray in photograph, yellow in section). Cellular detail is lost because of autolysis. Stain and magnification as in Fig. 13.

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Osteogenesis irnper[ecta

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Fig. 16. Spicules in region below conversion line of femur of patient. Material covering spicules of calcified cartilage matrix is intensely P. A.S. p o s i t i v e (black in photograph, deep red in section). (Periodic acidSchiff stain (P.A.S.). Original magnification same as in Fig. 13.) Fig. 15. Spicules in region below conversion line of femur of patient. Spicules of calcified cartilage matrix are covered by basophilic material (dark gray in photograph, blue in section) which resembles normal osteoid morphologically. Atypical osteoblasts similar to those seen in Fig. 13 are present. (Hematoxylin-eosin stain. Original magnification same as in Fig. 13.) gree of immaturity compatible with that seen in other organs. The striking feature of the kidneys was the presence of calcium deposits in the distal tubules. These deposits were widely spread throughout the medulla and gave a positive von Kossa stain. Fetal atelectasis and a minimal amount of aspirated amniotic contents were seen in sections of the lungs. In addition, there was a moderate degree of thickening of both the media and adventitia of the small and medium size pulmonary arteries. The elastic fibers in the media of these vessels were accordingly increased in number. DISCUSSION

T h e clinical triad of brittle bones, blue sclerae, a n d deafness is c o m m o n l y recognized as the h a l l m a r k of osteogenesis i m p e r fecta. These diverse features indicate that this disorder involves multiple systems. Alt h o u g h earlier investigators 7' s suspected that the basic defect in osteogenesis imperfecta lay in the f o r m a t i o n of tissues which were

mesenchymal in origin, the underlying comm o n d e n o m i n a t o r of the involved systems was largely u n k n o w n until the recent work of Follis 2-4 who has convincingly d e m o n s t r a t e d that there is a widespread failure in m a t u r a tion of connective tissue precursors both in collagen a n d in bone. I n the skin, cornea, and sclera this failure of m a t u r a t i o n is manifested by an increased n u m b e r of delicate reticulum fibers a n d the paucity of m a t u r e collagen. I n o u r case, the corium of the skin (Fig. 3), the cornea (Fig. 7), a n d the sclera (Fig. 9) were appreciably r e d u c e d in thickness and m a n y of the component fibers resembled reticulum both morphologically a n d histochemically (Fig. 5). I n bone the failure of m a t u r a t i o n is manifested by the deposition of an atypical osteoid which according to Follis 2-4 represents an i m m a t u r e form of bone matrix. T h e histochemical properties of this m a t e r i a l are qualitatively similar to those of reticulum in the corium and the eye. In addition, a b n o r m a l

9 1 4: Hreno and Haust

spindle-shaped osteoblasts were found within this atypical osteoid. (Figs. 13, 15, 16) T h e latter was apparently the product of these morphologically altered osteoblasts. In the diaphysis, the spongiosa was composed of thin delicate spicules, m a n y of which had persistent central cores of calcified matrix of cartilage. T h e increased fragility of this structure was indicated by the presence of complete fractures of the shaft (Fig. 2) and micro fractures of the individual spicules. At the site of fractures healing appeared to be proceeding normally. I n a recent study of a family affected by osteogenesis imperfecta, Stadii ~ described an abnormality in the elastic fibers of the corium. H e observed an increased n u m b e r of elastic fibers which showed a variable degree of degeneration. This abnormality was not observed in our case. W h e t h e r the increased n u m b e r of elastic fibers in the small- and medium-sized pulmonary arteries represents the same abnormality as described by Stadil a in the skin or simply is a part of the thickened media cannot be determined. Nephrocalcinosis is not a commonly reported lesion in premature infants. I n our patient calcium deposits were found in the distal tubules of both kidneys. Since these deposits could represent either metastatic or dystrophic calcification, the precise pathogenesis of these lesions was difficult to establish. Although no significant biochemical abnormalities of calcium and phosphorus are known to occur in osteogenesis imperfecta, foci of metastatic calcification in various tissues have been observed by other investigatorsS' ~ Therefore, the calcium deposits in the renal tubules may represent a form of metastatic calcification simply as a result of multiple healing fractures associated with a transient mobilization of body calcium stores. However, the possibility that these deposits may represent a form of dystrophic calcification cannot be excluded. Recently Brigham and Tourtellotte D have described 2 cases of osteogenesis imperfecta in which abnormaI urinary and plasma amino acid patterns suggestive of a renal tubular defect were found. Since the presence or absence of such a

June 1963

tubular defect cannot be established in our case, the calcium deposits may or m a y not represent a form of dystrophic calcification. It is of interest to note that some of the amino acids involved in the abnormal urinary and plasma patterns described by Brigham and Tourtellotte 9 are also found in large amounts in connective tissue. These investigators have suggested therefore, that perhaps some aberration in amino acid metabolism m a y be related to the etiology of the disease. Thus, the entity of osteogenesis imperfecta m a y belong to the broad group of diseases categorized as inborn errors of metabolism. SUMMARY

A case of osteogenesis imperfecta congenita has been described. Histochemical studies confirmed the concept that there is a lack of maturation of some of the connective tissue precursors. Nephrocalcinosis present in our case is an infrequently reported observation in this disease.

REFERENCES

1. McKusick, V. A.: tIeritable disorders of connective tissue, St. Louis, 1960, The C. V. Mosby Company, pp. 178-212. 2. Follis, R. H., Jr.: Osteogenesis irnperfecta congenita; a connective tissue diathesis, J. PEDIAT. 41: 713, 1952. 3. Follis, R. H., Jr.: Maldevelopment of the corium in the osteogenesis imperfecta syndrome, Bull. Johns Hopkins Hosp. 93: 225, 1953. 4. Follis, R. H., Jr.: Histochemical studies on cartilage and bone. III. Osteogenesis imperrecta, Bull. Johns Hopkins Hosp. 93: 386, 1953. 5. Ruedemann, A. D., Jr.: Osteogenesis imperfecta congenita and blue selerotics; a cllnicopathologic study, A. M. A. Arch. Ophth. 49" 6, 1953. 6. Stadil, P.: Histopathology of the corium in osteogenesis imperfecta, Danish M. Bull. 8: 131, I96I. 7. Bauer, K. H.: Ueber osteogenesis imperfecta, Deutsche Ztschr. f. Chir. 154: 166, 1920. 8. Weber, M.: Osteogenesis imperfeeta congenita. Arch. Path. 9: 984, 1930. 9. Brigham, M. P., and Tourtellotte, C. D.: Amino acid changes in blood and urine in osteogenesis imperfecta, Fed. Proc. 21: 167~ 1962.