Chondrodysplasia in twins.

Our colleague, L. G. Parsons', has briefly outlined the historical facts regarding a disorder of the skeleton bearing the various names-hereditary deforming chondrodystrophy, multiple cartilaginous exostosis, diaphysial aclasis (Keith) or Ollier's disease; and Brailsford' has recorded the radiological details of a similar condition under the term chondro-osteodystrophy. The disease produces a striking clinical picture and is of special interest in relationship to its congenital origin, familial tendency, and its more frequent occurrence in males. The essential disorder lies apparently in the abnormal process of bone growth, affecting the skeletal parts derived from a cartilaginous or membranous basis. Its cause is unknown. Although certain theoretical endocrine and peripheral vascular derangements have been suspected, no true evidence of such is established in cases carefully studied. From the pathological aspect ' the growth of cartilage appears to be excessive and the calcification irregular.' Radiographic studies of the long bones show the metaphysis and the end of the diaphysis to be occupied by cartilage, and the bone cortex in the same areas to be thin and irregular. The cartilaginous masses may thus, in some areas, give a pseudo-cystic appearance. The epiphysis is notably misshapen and reveals an unusual direction, usually oblique. Parson's description of the clinical picture epitomizes the significant features and he states that the clinical picture depends to a large extent on the presence or absence of secondary skeletal deformities; indeed, the presence of multiple exostoses may pass completely unnoticed by the patient, or attention may only be drawn to them by limitation of movement at a joint, or by pain from a pointed exostosis. All sorts of variations exist; thus in some cases there may be exostosis in normal bones, in others exostosis in bones with slight deformities, or in others again deformed bones without exostosis. If deformed bones are present the deformities become marked as the child grows, and there is always some stunting of growth, this being due to shortness of the legs. The arms are also shortened. The unequal growth in length of the paired bones of the legs and forearms produces characteristic deformities and radiographic changes. ' The radius becomes a bent bow; the ulna serves as its tight string. In about one-third of the cases the bow becomes unbent by a spontaneous dislocation of the proximal end of the radius '(Keith). Less