Mutations in USH2A in Spanish patients with autosomal recessive retinitis pigmentosa: high prevalence and phenotypic variation

etinitis pigmentosa (RP), which occurs in about one in 3000-7000 people in Spain, is inherited in an autosomal dominant manner in 12% of cases, in an autosomal recessive way in 39%, and in an X linked manner in 4% of cases. This leaves 41% of RP cases with a simplex form and 4% in which the transmission pattern is unclear. Mutations in the beta subunit of the rod cGMP-phosphodiesterase gene, 2-5 in the ATP binding cassette receptor gene, 6 and in the TULP1 gene 7 account for a small percentage of Spanish ARRP families. These data indicate that genes other than these may be involved in the remaining families, emphasising the genetic heterogeneity of the disease and reinforcing the hypothesis that in ARRP a number of genes rather than one major gene will account individually for a small number of cases.