Preclinical detection in Japanese families with myotonic dystrophy using polymorphic DNA markers.

Myotonic dystrophy (DM) is a genetic disease inherited by an autosomal dominant trait and characterized by multi-organ disorders. Although its biochemical basis has been unknown, the DM locus is closely linked to D19S19 and APOC2 on the long arm of chromosome 19 both in Japanese and Caucasian populations. Linkage studies of Japanese DM families using these polymorphic DNA markers detected two asymptomatic gene carriers in two unrelated families.