HIGH-INCIDENCE OF AUTOSOMAL RECESSIVE NONSYNDROMAL CONGENITAL RETINALNONATTACHMENT (NCRNA) IN AN IRANIAN FOUNDING POPULATION

In an isolated and founding Iranian population the prevalence of conge nital total blindness is 1.1%. Clinical findings such as lack of perce ption of light, massive retrolental mass, shallow anterior chamber and nystagmus, in otherwise normal individuals, correspond to nonsyndroma l congenital retinal nonattachment. To determine the inheritance of th is disease we constructed an extensive nine-generation pedigree of the affected kindred living in the Iranian founding population. The pedig ree, which includes 42 patients from 25 sibships, clearly suggests aut osomal recessive inheritance. To verify the inheritance, we compared t he average coefficient of inbreeding (F) of the affected sibships with that of the control sibships, calculated the patients' sex ratio, and also compared the observed relative frequency of the disease with its expected relative frequencies for different modes of inheritance. The patients' average F value is significantly greater than that of the c ontrols (P < 0,001), The sex ratio of the patients is close to unity a nd the observed relative frequency of the disease is close to that of an autosomal recessive trait, All these findings strongly support auto somal recessive transmission of this disease. (C) 1998 Wiley-Liss, Inc .