[A case of distal spinal muscular atrophy].

A 13-year-old boy with distal spinal muscular atrophy was reported. He noted atrophy of the bilateral legs since 11 years old. Ankle jerk was brisk and pes cavus was observed. Needle EMG of the leg showed denervation pattern. Muscle biopsy of the gastrocnemius muscle revealed large group atrophy and fiber type grouping. MCV, SCV and results of sural nerve biopsy were normal. We diagnosed his disorder as distal muscular atrophy. The essential lesion of this disease was supposed to be in the anterior horn cells.