Editor—Retinitis pigmentosa (RP) is the most common form of retinal dystrophy. Patients present with night blindness and progressive narrowing of the visual field, eventually leading to central vision loss. Fundus examination usually shows bone spicula pigmentation, attenuation of blood vessels in the retina, and waxy pallor of the optic disc. Typically, the electroretinogram is notably diminished or even abolished.1

RP shows important allelic and non-allelic genetic heterogeneity (RET-GEN-NET) with different modes of inheritance, including autosomal dominant (AD), autosomal recessive (AR), X linked, and digenic.

ARRP is the most common form of RP. A locus for ARRP,RP25, was mapped in 1998 to the long arm of chromosome 6 between microsatellite markers D6S257 and D6S1644 (MIM 602772).2 Recently, we have excluded two candidates,GABRR1 and GABRR2,as the disease causing gene.3

Several loci with retinal dystrophy phenotypes have been mapped to the pericentromeric region of chromosome 6. They include autosomal dominant Stargardt-like disease (STGD3),4 autosomal dominant macular atrophy (ADMD),5autosomal dominant …