A 56-year-old moderately obese woman is referred for evaluation and treatment of a rash affecting her lower abdomen and groin. The dermatitis has been present for approximately 1 year and occasionally burns and itches. Topical therapy with econazole cream was ineffective. Oral prednisone resulted in lightening, but the condition flared as the dose was tapered and the treatment discontinued. Examination revealed a well-demarcated, erythematous patch in the affected area. No abnormalities of the skin, hair, or nails were noted elsewhere.
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Inverse psoriasis, also known as flexural or intertriginous psoriasis, is a subtype of psoriasis that affects between 3% and 7% of patients.1 Inverse psoriasis characteristically presents in the flexural creases of the submammary folds, inguinal area, axillae, and gluteal folds.2 As the name implies, inverse psoriasis presents as the reverse of common psoriasis, which typically affects the extensor surfaces and scalp. Inverse psoriasis occurs more frequently in overweight or obese patients.3 Other exacerbating factors include infection, friction, and heat.4 Clinically, inverse psoriasis presents as an erythematous, well-demarcated dermatitis that extends to and ends at the skin fold junction. Due to the moist environment, the rash is devoid of the silvery scales commonly seen in traditional plaque psoriasis.3 Inverse psoriasis can be easily misdiagnosed as a fungal or bacterial infection such as candidiasis or erythrasma.2
Inverse and plaque psoriasis have similar histologic features.1 Diagnosis is based on history and physical examination; skin biopsy and bacterial/fungal cultures may be useful to narrow the differential. Topical mid- to low-potency corticosteroids may afford adequate control, but the former may induce striae with prolonged use.3 The topical immunomodulators tacrolimus and pimecrolimus may be used safely as long-term treatment.1 Additional treatments include ultraviolet B phototherapy and excimer laser. Refractory cases may benefit from biologic therapy.5 Aside from pharmacologic treatment, patients with inverse psoriasis are advised to practice proper hygiene and begin a regular exercise routine for weight management.
- Syed Z, Khachemoune A. Inverse psoriasis: case presentation and review. Am J Clin Dermatol. 2011;12(2):143-146.
- Gordon K., Ruderman E. Psoriasis and Psoriatic Arthritis: An Integrated Approach. 1st ed. New York, NY: Springer-Verlag Berlin Heidelberg; 2005:70-71.
- George N, Nichols K. Inverse psoriasis: a case report. Am J Nurse Pract. 2007;11(3):29-36.
- Weigle N, McBane S. Psoriasis. Am Fam Physician. 2013;87(9):626-33.
- Khosravi H, Siegel MP, Van Voorhees AS, Merola JF. Treatment of inverse/intertriginous psoriasis: updated guidelines from the Medical Board of the National Psoriasis Foundation. J Drugs Dermatol. 2017;16(8):760-766.