Roentgen Observations in Familial Metaphyseal Dysostosis

Abstract

Metaphyseal dysostosis is a disease with important genetic implications, characterized by selectively disturbed endochondral bone formation leading to reduced stature. As in achondroplasia and other conditions simulating it, the extremities are chiefly affected, resulting in a disproportionate dwarfing which spares the trunk. Roentgen investigation often yields appearances easily confused with other diseases affecting bone development. Calcium and phosphorus metabolism and osteoblastic activity are normal, yet radiographic similarities to resistant rickets and other metabolic abnormalities have led to mistaken diagnoses and treatment with high doses of vitamin D without benefit and occasionally with some unnecessary complications (2). It is apparent, therefore, that awareness of the disease spectrum is important for accurate roentgen interpretation. We have recently had the opportunity of studying several patients and families affected by this condition. Some unique features observed form the basis of this report. Literature Metaphyseal dysostosis was first described as an entity by Murk Jansen in 1934 (6). Sporadic reports in the European and American literature since that time have added 2 additional cases (3, 5, 14). In Jansen's case the disease displayed a rather severe involvement of the metaphyses of all long bones, including the tubular bones of the hands and feet. As has proved to be a characteristic of all subsequently documented cases, the epiphyses are remarkably uninvolved and reveal normal development and structure. The skull and spine are usually unaffected. Rarely there is abnormality of the flat bones (3). In the Jansen type, metaphyseal changes can be striking and often lead to severe deformity and disability, and possibly early death. The extreme rarity of this form, however, has precluded adequate study and clear definition of the entire clinical picture. A milder form of metaphyseal disorder was noted in 1949 when Schmid described an expression of the disease which has proved to be far more common among cases recently recorded in the literature (13). In these, the metaphyseal changes may be quite minimal, yet nonetheless lead to moderately reduced stature and gait disturbance. In the Schmid type only the major long bones are usually involved, and changes in the tubular bones of the hands and feet are much less frequent than in the Jansen type. Characteristically, the infants appear normal at birth but as they begin to walk, a triad of waddling gait, bowed legs, and short stature becomes apparent. The epiphyseal ends of the bones and joints frequently appear enlarged clinically but only occasionally is there evidence of associated pain or tenderness. Following clinicalexamination and radiographic studies, often a nutritional or metabolic deficiency is suspected. In a number of cases treatment with vitamin D has been instituted without benefit.