Inverse psoriasis, also called flexural psoriasis, is a variation of psoriasis, which is an autoimmune disease. It affects the skin and manifests as shiny red patches in places where the skin folds. Inverse psoriasis can show up under the armpits, in between the buttocks, beneath the breasts, or in the groin area. Although lacking the scales that are characteristic of plaque psoriasis, inverse psoriasis is still extremely itchy and painful. Because this type of psoriasis often appears in the groin and armpit area, it is frequently misdiagnosed as a yeast or fungal infection. Ironically, if inverse psoriasis is left untreated, yeast and fungal infections often do develop as a secondary skin infection.