Segregation and sporadic cases of Duchenne muscular dystrophy in the Henan Province, China.

In the Henan province, China, the segregation ratio of Duchenne muscular dystrophy, estimated through classical segregation analysis on 103 sibships, is p = 0.462, and the maximum likelihood proportion of sporadic cases is x = 0.264. These figures are in agreement with the results of segregation analysis on 1,800 families from different countries; also, the Henan population shows a slight segregation distortion and lacks a fraction of the sporadic cases predicted under mutation-selection equilibrium. Although not statistically significant, the downward departure of the estimated parameters from their expectations under the mendelian equilibrium hypothesis (p = 0.5; x = 0.333) confirms an anomalous segregation pattern for Duchenne muscular dystrophy. A possible role of germinal mosaicism in concealing a fraction of sporadic cases is discussed.