Retinitis pigmentosa in Spain. The Spanish Multicentric and Multidisciplinary Group for Research into Retinitis Pigmentosa.

Retinitis pigmentosa is a term commonly given to a group of inherited and progressive disorders which affect the photoreceptors of the retina. As part of an ongoing research programme throughout Spain, clinical, epidemiological, and genetic studies have been carried out on these diseases. Here, we report the relative frequencies of the different genetic types in 503 non-syndromic and 89 syndromic RP families of Spanish origin. The most frequent syndromic RP forms were Usher syndrome type 1 (20/89 families = 30%) and Usher syndrome type 2 (44 families = 49%). Among non-syndromic RP forms, 12% were autosomal dominant, 39% autosomal recessive and 4% X-linked. Forty-one percent were isolated or simplex cases and in 4% the genetic type could not be established.