Genetic aspects of retinitis pigmentosa in China.

We analyzed 151 pedigrees (209 cases) of retinitis pigmentosa in Shanghai, China. Of the 209 cases, the proportion of autosomal recessive (AR), autosomal dominant (AD), X-linked recessive (XR), and simplex cases is 33.1, 11, 7.7, and 48.3% respectively. The average age of onset was 24.7 years in the AD type, 22.9 years in the AR and five years in the XR type. The average refractive errors were -1.88 D in the AD type, -2.37 D in the AR type, and -5.72 D in the XR type. In addition, 24,100 persons were screened and six cases of retinitis pigmentosa were found. The gene frequencies of the AR (including simplex cases), AD, and XR types as calculated from the disease prevalence were 0.0142267, 0.0000137, and 0.0000384, respectively. The gene frequency of the AR type as calculated from the frequency of consanguinity (15.9%) was 0.00389, which is much less than that calculated from the prevalence. The probable explanation is that the AR type of retinitis pigmentosa really consists of several different disease entities, with each entity representing a separate gene mutation. The number of different mutations within the AR group is estimated to lie between 11 and 41.