Natural history, presentation, and diagnosis of hidradenitis suppurativa.

The diagnosis of hidradenitis suppurativa (HS) is based on a characteristic history and physical exam. The anatomic sites of involvement include the axillae (most common), groin, and buttocks, and the perianal, perineal, and mammary regions. Initially, HS manifests with open comedones (usually with two or more "heads") and tender subcutaneous acneiform papules. Without intervention, the natural history of HS is chronic and progressive. More painful subcutaneous nodules form, which rupture and drain a thick, mucopurulent, foul-smelling fluid. Later, sinus tracts form, and, over time, ropelike fibrotic subcutaneous scarring occurs, which can lead to disabling contractures of the affected limbs. Clinically, the severity of disease is classified using the Hurley staging system, which provides guidance for choosing among treatment options.