Calf hypertrophy in spinal muscular atrophy

Two unusual variants of spinal muscular atrophy with gross calf hypertrophy of adolescent onset were studied clinically, electrophysiologically and histologically. There have been reports of several variants within this group of spinal muscular atrophies. In Singapore we encountered 2 patients who had an unusual variant of spinal muscular atrophy not well recognised previously with only 3 reports recorded to date. Our cases presented with gross calf hypertrophy and a slowly progressive clinical course. Nerve conduction studies were normal but electromyogram and muscle biopsies revealed a chronic denervation problem of probable central origin.