Genetic epidemiology of Duchenne muscular dystrophy in Japan: classical segregation analysis.

Classical segregation analysis was performed on 651 male probands in 597 families with Duchenne muscular dystrophy (DMD) collected from 20 of 25 National Institutions for Muscle Diseases in Japan. The proportion of sporadic cases is compatible with 1/3 expected for an X-linked lethal trait with an equal mutation rate in egg and sperm, the estimated mutation rates being 9.2 X 10(-5) and 10.9 X 10(-5)/gamete/generation, respectively. The incidence and prevalence among males were estimated to be 29.2 X 10(-5) and 6.7 X 10(-5), respectively. These results indicated no difference from the patterns of DMD in Western countries.