[Mutational and clinical features of Japanese patients with dysferlinopathy (Miyoshi myopathy and limb girdle muscular dystrophy type 2B)].

Mutations in the dysferlin gene cause both Miyoshi myopathy (MM) and limb girdle muscular dystrophy 2B (LGMD2B). We examined patients with dysferlinopathy in Japan, and identified 28 and 12 different mutations respectively in MM and LGMD2B patients. The mean age at onset of the patients with MM was 22 +/- 9 years (range 12-48 years) and that of the patients with LGMD2B was 26 +/- 10 years (range 11-43 years). On the average, the first use of a cane was at 33 years (14 years after the onset) for MM and 39 years (15 years after onset) for LGMD 2B. Patients became wheelchair-bound at 41 years (21 years after onset) in MM and 45 years (21 years after onset) for LGMD2B. The mean maximum serum CK level at any age of the patients was 5,829 +/- 4,273 IU/l (range 1,289-12,566 IU/l ) for MM and 3,787 +/- 2,493 IU/l (627-10,000 IU/l) for LGMD2B: in both disorders, the serum CK level fell in proportion to the duration of the illness. We have identified four common four mutations (C1939G, G3370T, 3746delG, and 4870delT) in Japanese patients with MM, accounting for 48 percent of all MM mutations in this population. Two of the four mutations (G3370T, and 4870delT) accounted for 52 percent of the mutations in LGMD2B patients, while the 3746delG mutation was not found in patients with LGMD2B. The G3370T mutation may be associated with a milder form of MM and LGMD2B. By contrast, the G3510A mutation appears to be associated with a severe form of MM.