MULTICENTER GENETIC-STUDY OF RETINITIS-PIGMENTOSA IN JAPAN .1. GENETIC-HETEROGENEITY IN TYPICAL RETINITIS-PIGMENTOSA

A nationwide, multicenter study of typical retinitis pigmentosa (RP) w as carried out in collaboration with 18 hospitals throughout Japan to obtain current information for genetic counseling. We analysed the gen etic heterogeneity of RP based on the parental consanguinity of 434 pr obands registered during a 6-month period in 1990. A gradual decline i n the frequency of consanguineous marriage was recognized among the no rmal parents of RP patients. The relative frequencies of inheritance p atterns were estimated as: autosomal recessive, 25.2%; autosomal domin ant, 16.9%; X-linked, 1.6%; and simplex, 56.3%. A comparison of these results with previous reports in Japan revealed a decline in the relat ive frequency of autosomal recessive cases and an increase in simplex cases. This suggests a decrease in the incidence of autosomal recessiv e retinitis pigmentosa in Japan, as well as the necessity for exhausti ve investigations aimed at identifying inheritance patterns for RP pat ients seeking genetic councelling. (C) 1997 Japanese Ophthalmological Society.