Epidemiology

Worldwide, the estimated prevalence of all forms of retinitis pigmentosa (RP) is 1 in 4000.[6][7]​​​​​​​​ Population-based studies report a relatively higher prevalence of 1 in 750 in India (1 in 372 in the rural setting and 1 in 930 in urban areas).[8][9]​ A presumed period prevalence of 1 in 6500 has been reported in South Korea; incidence of RP was found to be 1.64 cases per 100,000 person-years.[10]

The rates of autosomal dominant (ADRP), autosomal recessive (ARRP), and X-linked (XLRP) RP vary considerably from region to region. A study of medical and social service sources in Maine reported rates of 19% ADRP, 65% ARRP, and 8% XLRP.[11] Mass screening in China revealed rates of 5.2% ADRP, 3.0% XLRP, and 91.8% ARRP.[12] In a series from the UK, rates were 39% ADRP, 25% XLRP, and 36% ARRP.[13] The age of onset is variable and depends on the mutation involved.[6]

X-linked RP primarily affects males and is associated with early onset and severe disease.[14] Female carriers may exhibit a wide range of atypical and/or asymmetric disease due to random x-inactivation.[15] While some female carriers may have subclinical disease and be asymptomatic, others may exhibit severe disease with classic features of RP.[15][16]​​

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