RETINITIS-PIGMENTOSA IN INDIA - A GENETIC AND SEGREGATION ANALYSIS

Seventy-eight families with retinitis pigmentosa, presenting at the ge netic clinic of Sankara Nethralaya, Madras, over a period of 6 months (from April to September 1993), were assessed to determine the differe nt genetic types: 9% were autosomal dominant; 36%, autosomal recessive ; 3%, X-linked recessive; 44%, isolated cases and 8%, undetermined gen etic type. A high incidence of consanguinity was observed in autosomal recessive (57%) and isolated cases (37%). Segregation analysis showed good agreement in autosomal dominant (chi(2)=0.864) and recessive fam ilies (p=0.222). The high proportion of autosomal recessive and isolat ed cases in this study, when compared with other similar studies, is d ue to the high incidence of consanguineous marriages in the Indian sub continent.