USH2A and retinitis pigmentosa 1: In their study they found that some missense USH2A alleles (among them, the p.(Cys759Phe) variant) were confined to nonsyndromic RP cases, being enriched in nonsyndromic RP compared to USH2 cases, whereas "null" variants were rare in nonsyndromic cases and common in USH2 (as in the present series).