High incidence of autosomal recessive nonsyndromal congenital retinal nonattachment (NCRNA) in an Iranian founding population

Abstract

In an isolated and founding Iranian population the prevalence of congenital total blindness is 1.1%. Clinical findings such as lack of perception of light, massive retrolental mass, shallow anterior chamber and nystagmus, in otherwise normal individuals, correspond to nonsyndromal congenital retinal nonattachment. To determine the inheritance of this disease we constructed an extensive nine-generation pedigree of the affected kindred living in the Iranian founding population. The pedigree, which includes 42 patients from 25 sibships, clearly suggests autosomal recessive inheritance. To verify the inheritance, we compared the 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 controls (P < 0.001). The sex ratio of the patients is close to unity and the observed relative frequency of the disease is close to that of an autosomal recessive trait. All these findings strongly support autosomal recessive transmission of this disease.