Epidemiology

Retinitis pigmentosa (RP) is the most common form of inherited retinal disease worldwide, with an the estimated global prevalence of 1 in 4000.[6]​​[7]​​​​​​[8]​ However, prevalence varies by country. 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).[9][10]​​​​​ A prevalence of 1 in 6500 has been reported in South Korea, and 1 in 1700 in Singapore.[11][12]​​​​ In Europe, prevalence has been reported as approximately 1 in 3000-4000 in Denmark and Norway, and <1 in 7000 in Spain.​​​​​​​​[6]

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.[13] Mass screening in China revealed rates of 5.2% ADRP, 3.0% XLRP, and 91.8% ARRP.[14] In a series from the UK, rates were 39% ADRP, 25% XLRP, and 36% ARRP.[15] 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.[16] Female carriers may exhibit a wide range of atypical and/or asymmetric disease due to random x-inactivation.[17] While some female carriers may have subclinical disease and be asymptomatic, others may exhibit severe disease with classic features of RP.[17]​​​[18]

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