A 72-year-old man is referred for evaluation of a rash involving his perianal region. He states that the condition has waxed and waned in intensity over the past 20 years and has been treated intermittently with topical corticosteroids and/or topical antifungals. On occasion, the rash may itch or burn. He is currently applying betamethasone dipropionate cream. Physical examination reveals a well-demarcated zone of erythema in the perianal region. Other than a scaly patch of his posterior scalp, no similar findings are noted elsewhere.
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Psoriasis is a chronic skin disorder that most frequently manifests on the elbows, knees, lower back, and scalp. The condition is characterized by sharply marginated plaques with varying degrees of silvery-white overlying scale.1 The condition is caused by underlying immune dysfunction that involves the interaction of T cells with dendritic cells, macrophages, and keratinocytes activated by several classes of cytokines.2 Psoriasis is one of the most common skin disorders affecting approximately 3% of the US population or more than 7.5 million adults.3
Psoriasis in the perianal and intergluteal regions can be associated with pain and itching.4 Scaling may be minimal or absent and the condition may be accompanied by intense redness and fissuring.5 Other conditions that may present as persistent perianal dermatitis in an adult include contact dermatitis and extramammary Paget’s disease.6,7 Workup may include skin patch testing and biopsy.5
Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Geisinger Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
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3. Armstrong AW, Mehta MD, Schupp CW, Gondo GC, Bell SJ, Griffiths CEM. Psoriasis prevalence in adults in the United States. JAMA Dermatol. 2021;157(8):940-946. doi:10.1001/jamadermatol.2021.2007
4. Farber EM, Nall L. Perianal and intergluteal psoriasis. Cutis. 1992;50(5):336-338.
5. Gisondi P, Bellinato F, Girolomoni G. Topographic differential diagnosis of chronic plaque psoriasis: challenges and tricks. J Clin Med. 2020;9(11):3594. doi:10.3390/jcm9113594
6. Agulló-Pérez AD, Hervella-Garcés M, Oscoz-Jaime S, Azcona-Rodríguez M, Larrea-García M, Yanguas-Bayona JI. Perianal dermatitis. Dermatitis. 2017;28(4):270-275.
7. Lopes Filho LL, Lopes IM, Lopes LR, Enokihara MM, Michalany AO, Matsunaga N. Mammary and extramammary Paget’s disease. An Bras Dermatol. 2015;90(2):225-231. doi:10.1590/abd1806-4841.20153189