Muscle involvement in progressive diaphyseal dysplasia.

Muscle involvement in progressive diaphyseal dysplasia was evaluated in five children, of whom four were members of one family. Age range was 2 to 10 years 9 months, and mean age was 5.5 years. Evaluation included serum enzymes, electromyography, and muscle biopsy examined by light and electron microscopy. Serum enzymes were usually noncontributory. Electromyography revealed "myopathic pattern" in four of the five patients. Muscle biopsy specimens were taken from three of the five children, including two patients from one family, of whom one had normal electromyography, and one sporadic case. Examination of the biopsy specimens by light microscope was generally not useful, whereas electron microscopic examination revealed myopathic and vascular changes consisting of atrophy of isolated muscle fibers, accumulation of endomysial collagen fibrils, and thickening of the perivascular basement membrane. The main contribution of this study is to describe electron microscopic vascular changes in muscles that appear to be similar in familial and sporadic cases of progressive diaphyseal dysplasia.