Is there genetic heterogeneity in Usher's syndrome?

Usher's syndrome is an autosomal recessive disease characterized by congenital sensorineural hearing loss and retinitis pigmentosa (RP). Evidence for genetic heterogenicity within a single pattern of transmission of RP, be it autosomal recessive, dominant or sex-linked recessive, has been demonstrated by clustering patterns within and between families of specific clinical parameter weightings. Fishman, et al have noted corresponding evidence for subtypes of Usher's Syndrome, of paramount importance in mounting molecular level studies elucidating pathogenesis and management. Our study is of 25 consecutive patients studied by clinical investigation, including audiometric, vestibular and electro-ocular tests. Evidence for and against horizontal as well as proximal to distal receptors is weighed against loss of both visual and cochleo-vestibular systems. The clinical relevance is discussed.