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Author: Dr Priyam Sobarun, Dermatology Registrar, Waikato Hospital, Hamilton, New Zealand; Copy Editor: Clare Morrison; Chief Editor: Dr Amanda Oakley, June 2014.
Psoriasis is a common, long-term scaly skin condition that affects approximately 2% of the population. Genital psoriasis affects the genital skin, which includes the pubic area, vulva or penis, skin folds including natal cleft, and buttocks. It is known as anogenital psoriasis when psoriasis also affects perianal skin. Psoriasis does not affect mucosal surfaces.
Psoriasis is one of the most common diseases affecting anogenital skin. It can be part of more generalised plaque psoriasis, but it may also be the only affected area in 2–5% of cases. Rarely, generalised and localised pustular psoriasis can also affect the genital skin.
Genital skin can also be affected in inverse or flexural psoriasis, psoriasis that mainly affects the skin folds. Genital psoriasis may be associated with considerable discomfort and embarrassment, and may severely impair the quality of life and sexual well-being of those affected.
Genital psoriasis affects males and females, children and adults. In children, genital psoriasis is most common under the age of 2, when it presents as psoriatic napkin eruption.
Psoriasis of the external genitalia and perianal area often presents as well-demarcated, bright red, thin plaques. These usually lack scale, as friction between the skin surfaces rubs it off. Scales may be seen on the outer parts of the genital skin. Scales can be easily scraped off, leaving pinpoint bleeding.
In women, vulval psoriasis appears symmetrical. It can vary from silvery, scaly patches adjacent to the labia majora to moist, greyish plaques or glossy red plaques without scaling in the skin folds.
In men, the penis and scrotum may be involved. The glans penis, the bulbous part of the end of the penis, and the corona (the base or "crown" of the glans) are most commonly affected. In circumcised men, plaques can be more scaly than on the rest of the genital skin. In uncircumcised men, nonscaling plaques are more common.
Psoriatic napkin eruption presents as red and sometimes silvery plaques with well-defined borders in the nappy area of children under the age of 2 years. It usually clears up after a few months to a year, but may later generalise into plaque psoriasis.
Psoriasis in genital areas can be very itchy at times. The plaques may also be fissured and painful.
Psoriasis does not lead to scarring. The skin can return to a normal appearance with treatment or spontaneously.
Genital or anogenital psoriasis may be part of more generalised psoriasis. Psoriasis has multifactorial genetic and environmental causes. These are not fully understood. In the anogenital area, specific factors to consider include:
Psoriasis in the genital area may also be worsened by contact with irritants such as:
The diagnosis of psoriasis is usually made by its clinical appearance, with symmetrical, circumscribed erythematous plaques. Laboratory tests such as swabs and skin biopsies are rarely necessary.
Histologically, there is no apparent difference between ano and non-genital psoriasis.
Treatment of genital psoriasis is individualised. There is limited published data for efficacy and safety of treatment options. The following suggestions for treatment of genital psoriasis are based on expert opinions and case reports.
Vitamin D analogues such as calcipotriol cream can be cautiously used alone or in combination with topical steroids. However, they may irritate genital skin.
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