Genetic segregation analysis of retinitis pigmentosa

: Comprehensive genetic segregation analysis performed in 150 pedigree of retinitis pigmentosa (RP) showed that the disease manifested genetic heterogeneity. Families of the mating type Affected x Normal were autosomal dominant (AD), with 80% of penetrance and no sporadic cases. Families of the mating type Normal x Normal were 80% autosomal recessive (AR), with 20% of sporadic cases. In the present series, the RP pedigrees were AD in 13.3%, X-linked in 2.7%, AR in 67.3% and sporadic in 16.7%, and most sporadic cases were nongenetic. It was also demonstrated that, with the conventional mode of pedigree analysis, the proportions of AR and AD cases were underestimated, and the proportion of sporadic RP was overestimated.