Abstract
Introduction Inverse psoriasis affects the skin of flexural areas, such as the groin, axillae,
umbilicus, intergluteal fold, and external genitalia.
Clinical Case We herein report the case of a man who presented with anal pruritus and, upon physical
examination, a perianal dermatosis was found, which was characterized by erythematous
plaques, with fine scaling. The case was initially managed with zinc oxide, and when
no improvement was observed, we decided to take an incisional biopsy, which indicated
histological changes suggestive of psoriasiform dermatitis.
Discussion Inverse psoriasis affects 3% to 7% of patients with psoriasis, and it manifests with
erythematous plaques without the classic scaling appearance. The skin in these areas
is susceptible to maceration, irritation, and ulceration, which alter the classic
clinical picture. It may present with typical lesions or, less frequently, in isolation
in the anogenital region. In the anogenital presentation only, the diagnosis should
be made by biopsy, looking for the classic histopathological features of psoriasis.
As for the first-line treatment, low- or medium-potency topical steroids are used
for short periods of time; the second-line treatment is with emollients and tar-based
products; and the third-line treatment uses an immunomodulator.
Conclusion This presentation is infrequent, and it requires a high index of suspicion for the
diagnosis, always supported by biopsies, in search of the classic histopathological
features of psoriasis.
Keywords
perianal psoriasis - inverse psoriasis - perianal pruritus
