Subcorneal Pustular Dermatosis

Subcorneal pustular dermatosis (SPD) is a rare skin disease in which pus-filled pimples or blisters (pustules) form under the top (subcorneal) layer of the skin. It is most common in middle-aged adults (particularly women) but can develop in children. Pustules usually appear over a few hours and grow together to form round or wavy patterns. They most often form in areas where the skin may touch or rub together, such as the groin area, underarms, inside the elbows, and behind the knees. The pustules may be mildly itchy or painful, but despite being pus filled, are not infected. The diagnosis of SPD is made based on the appearance of the pustules and the  results of a skin biopsy (histologic findings). The cause of SPD is not known. There is currently no evidence it is inherited (no familial cases have been reported) and it is not contagious. SPD may be associated with other diseases or health problems including several autoimmune diseases, blood (hematologic) diseases, infections, and cancers. Rarely, it has been associated with taking certain medications (drug-induced SPD). SPD may be treated with is oral dapsone, which often improves symptoms within one month. However, the pustules may return when treatment is stopped. Other therapies have been tried with mixed results. While SPD may cause discomfort and cosmetic concerns, it typically does not affect overall health.