[Myotonic dystrophy type 2].

Myotonic dystrophies (DMs) are autosomal dominant disorders with multisystemic clinical features. DMs are categorized as DM1, caused by a (CTG)n expansion mutation in 19q13, and DM2, caused by a (CCTG)n expansion mutation in 3q21. The clinical features of DM2 are diffuse and proximal dominant weakness, wasting, myotonia, cardiac problems, cataracts, and insulinresistance. DM2 is milder than DM1. We compared the clinical features of both DMs and studied a Japanese patient with DM2 who had expansion mutations different from those usually attributed to the disease and originally discovered by European researchers. The detailed clinical features of the Japanese DM2 patient are described.