Autosomal recessive generalized myotonia

Four cases of autosomal recessive generalized myotonia are reported. Attention is drawn to the fact that this condition represents a disease entity distinct from the myotonia congenita of Thomsen, which is transmitted as an autosomal dominant trait. The clinical features of the two conditions are similar, apart from minor quantitative differences. The family history is the major tool for the differential diagnosis. The possibility of the detection of heterozygotes by electromyography is discussed.