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We have performed histochemical, immunohistochemical, electron microscopic, and biochemical studies on the upper tibial cartilage from a case of multiple epiphyseal dysplasia, Fairbank type. Most chondrocytes had intracytoplasmic inclusions which took the stains for proteins and were resistant to microbial collagenase digestion. The electron microscopic study showed that the inclusions are dilatations of the rough endoplasmic reticulum containing a material with alternately wide electron dense and electron lucent layers. Both in optical and in electron microscopy the inclusions fixed antibodies against the core protein of the large cartilage proteoglycans (aggrecans). They didn't stain with antibodies against type II collagen. The gel electrophoretic pattern of the large proteoglycans was different from normal controls. The morphologic and biochemical alterations found in multiple epiphyseal dysplasia are similar to those already described in pseudoachondroplasia (Stanescu et al.: Eur J Pediatr 138:121-225, 1982; Stanescu et al.: J Bone Joint Surg 66A:817-836, 1984). However, the inclusions are smaller and the growth cartilage much less disorganized in multiple epiphyseal dysplasia. The similarity of morphologic and biochemical abnormalities strongly suggests that the two diseases have a similar pathogenesis and belong to the same bone dysplasia family.

Fragilitas ossium, fro, is an often lethal recessive mutation that was discovered in a randombred stock of mice after treatment with the chemical mutagen tris(1-aziridinyl) phosphine-sulphine. The fro/fro mice have osteoporosis-bending and fracture of the long bones-that is associated with apparently normal cartilage growth. The roentgenological and pathological features are similar to those of the severe, often lethal recessive form of human osteogenesis imperfecta.

The name opsismodysplasia is proposed for a new chondrodysplasia, which was studied in three patients. Clinically, the condition is recognized at birth on the basis of shortness, short hands, and facial abnormalities with a short nose and a depressed bridge of nose. The most characteristic radiographic signs are: very retarded bone maturation; marked shortness of the bones of the hands and of the feet with concave metaphyses; and thin, lamellar vertebral bodies. The growth cartilage studied in one case showed a wide hypertrophic area containing thick connective tissue septa, irregular provisional calcification, and vascular invasion. Type I collagen was detected in the hypertrophic area by immunohistochemical and microchemical tests. The transmission of opsismodysplasia is probably autosomal recessive.

Three patients with short stature, joint laxity, and peculiar pelvic radiology are described. The first case is similar to those described by Desbuquois et al., with deviation of digitis and supernumerary metacarpal bones. The other two children are less severely affected and are compared with others reported in literature. The authors suggest the homogeneity of the Desbuquois syndrome in spite of the variability of expression.

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