Inverse psoriasis

Inverse psoriasis, also known as flexural or intertriginous psoriasis, is a rare form of psoriasis. It can affect any location where two skin areas can rub against each other, most commonly involving the axillary, inframammary, groin, and intergluteal regions. Inverse psoriasis is considered “inverse” because it targets the flexure surfaces, whereas psoriasis classically affects the extensor surfaces (Van de Kerkhof et al. 2007). Psoriasis typically produces erythematous scaly plaques. Inverse psoriasis, on the other hand, creates bright erythematous, well-defined patches (Wolff et al. 2013). The presence of these lesions in the intertriginous areas is often a source of psychosocial stress. Inverse psoriasis appears to be undertreated and underreported, as many patients feel uncomfortable and do not seek help from their physicians (Omland and Gniadecki 2015). Therefore, it is important to be able to diagnose and treat inverse psoriasis as it can negatively impact the quality of life for these patients.

A psoriasis etiology may be overlooked in these patients because the lesions lack the characteristic scaling that is seen in psoriasis. The lesions may or may not be pruritic and appear smooth (Syed and Khachemoune 2011). The skin in intertriginous areas is often less keratinized and contains more sweat glands compared to sites of the body that are typically affected by psoriasis (Omland and Gniadecki 2015). The shiny appearance and decreased presence of scales is mainly due to the perspiration and friction in the body folds (Syed and Khachemoune 2011). The presentation of psoriasis in patients with HIV is often inverse psoriasis. Additionally, there has been an association between obesity and the diagnosis of inverse psoriasis (Omland and Gniadecki 2015). No histologic difference has been discovered between inverse psoriasis and psoriasis. It has not been reported that inverse psoriasis has a separate prognosis than psoriasis (Van de Kerkhof et al. 2007). Also, there has been no distinction noted in the T-cell-mediated inflammatory process in inverse psoriasis and psoriasis (Syed and Khachemoune 2011; Ghoreschi et al. 2007). Overall, there have been no clear findings that indicate a difference in the pathogenesis between inverse psoriasis and psoriasis. Of note, patients with inverse psoriasis often simultaneously have psoriatic lesions on other body areas (Van de Kerkhof et al. 2007). Thus, the detection of psoriatic lesions on other sites of the body helps in the diagnosis of intertriginous psoriasis.