Homozygosity mapping and linkage analysis demonstrate that autosomal recessive congenital hereditary endothelial dystrophy (CHED) and autosomal dominant CHED are genetically distinct

Background-Congenital hereditary endothelial dystrophy (CHED) is a corneal dystrophy characterised by diffuse bilateral corneal clouding resulting in impaired vision. It is inherited in either an autosomal dominant (AD) or au tosomal recessive (AR) manner. The AD form of CHED has been mapped to the p ericentromeric region of chromosome 20. Another endothelial dystrophy, post erior polymorphous dystrophy (PPM),has been linked to a larger but overlapp ing region on chromosome 20. A large, Irish, consanguineous family with AR CHED was investigated to determine if there was linkage to this region. Methods-The technique of linkage analysis with polymorphic microsatellite m arkers amplified by polymerase chain reaction (PCR) was used. In addition, a DNA pooling approach to homozygosity mapping was employed to demonstrate the efficiency of this method. Results-Conventional genetic analysis in addition to a pooled DNA strategy excludes linkage of AR CHED to the AD CHED and larger PPMD loci. Conclusion-This demonstrates that AR CHED is genetically distinct from AD C HED and PPMD.