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PERIANAL DISEASE

Many dermatoses, such as psoriasis, may affect the perianal skin as part of a more generalized eruption, or occasionally in isolation. Lichen planus conned to the mouth and genital–perianal region (orogenital lichen planus) is a particularly therapy-resistant variant. Crohn disease may present at this site (see Ch.11). Furunculosis, hidradenitis suppurativa,
and warts are also common problems in the perianal skin. All these are discussed more generally in other chapters.

Pruritus ani

This is a common and often intractable problem that, in many cases, seems to be due to minor degrees of leakage of fecal fluid on to the perianal skin. Burning pain and itch, often intense, are presenting features. This, and the scratching and rubbing that it provokes, may lead to lichenification and secondary eczematization. Threadworm infestation may need to be excluded, and occasionally psoriasis or a contact dermatitis (e.g. to medicated wipes). The mainstay of treatment is an effective barrier preparation combined with good hygiene, avoidance of soaps, and topical corticosteroids to treat the secondary eczematization. The patient should be encouraged not to scratch.

Perianal cellulitis

This condition (also confusingly termed perianal dermatitis) is usually due to streptococci. It presents as well-demarcated perianal erythema, which may be accompanied by itching, bleeding, and painful defecation (see Fig. 20.74).

Miscellaneous

Nicorandil can cause a chronic perianal ulcer. Discontinuing the drug heals the lesion.

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.