Autosomal dominant muscle cramp syndrome in a Japanese family

Objectives-To identify the clinical, electrophysiological, histological, and genetic characteristics of a Japanese family with a muscle cramp syndrome. Methods-Fourteen patients (eight men, six women) were studied in four generations of a single family. Electrophysiological examinations were performed in four cases and muscle and nerve biopsies were performed on the propositus. Results-The mode of inheritance seemed to be autosomal dominant. The cramps occurred during both exertion and at rest, and during sleep. Electromyographic examination indicated a neurogenic aetiology. There was a decreased number of large myelinated fibres in the sural nerve, and fibre type grouping in the quadriceps femoris muscle biopsy. Conclusions-The autosomal dominant muscle cramp syndrome in this family is probably caused by a polyneuropathy.