Screening for homozygosity by descent in families with autosomal recessive retinitis pigmentosa.

Retinitis pigmentosa (RP) is a genetically heterogeneous disease and an important cause of blindness in the state of Andhra Pradesh in India. In an attempt to identify the disease locus in families with the recessive form of the disease, we used the approach of screening for homozygosity by descent in offspring of consanguineous and nonconsanguineous families with RP. Microsatellite markers closely flanking 21 known candidate genes for RP were genotyped in parents and affected offspring to determine whether there was homozygosity at these loci that was shared by affected individuals of a family. This screening approach may be a rapid preliminary method to test known loci for possible cosegregation with disease.