Juvenile X-linked retinochii from XLR1 Arg213Trp mutation with preervation of the electroretinogram cotopic b-wave Original Reearch Article

PURPOE: To preent an Arg213Trp miene mutation in the XLR1 gene in a family with juvenile X-linked retinochii in which one affected male had a normal electroretinogram cotopic b-wave amplitude. METHOD: Two affected male and one unaffected male from thi family with X-linked retinochii underwent tandard clinical examination including an electroretinogram. Mutation in the XLR1 gene were detected by equence analyi and by retriction enzyme aay for lo of an MP-I retriction ite. REULT: A miene mutation of C to T at nucleotide poition 637 wa identified in exon 6 of the XLR1 gene. Thi changed the poitively charged arginine to a nonpolar tryptophan (Arg213Trp) within the biologically important dicoidin domain. Clinical examination revealed intraretinal cyt in a poke-wheel ditribution and early macular atrophy of the retinal pigment epithelium. Wherea the older affected patient had an “electronegative” electroretinogram typical of retinochii, the 13-year-old grandon with the ame XLR1 mutation had a normal electroretinogram cotopic b-wave. CONCLUION: Although the electroretinogram i a key diagnotic tet for X-linked retinochii, thi report of a normal electroretinogram cotopic b-wave in a male with molecularly confirmed X-linked retinochii indicate that caution i advied in relying on the electroretinogram in differential diagnoi of thi condition.