[Draining sinus in acne and rosacea. A clinical, histopathologic and experimental study].

The draining sinus is an unpleasant complication of acne conglobata, acne fulminans, acne inversa, rosacea conglobata and rosacea fulminans (pyoderma faciale). It is most common on the face, especially in the nasolabial folds, and on the neck below the mandibular line. Clinically, it is an elongated (2-5 cm long), elevated, periodically inflamed lesion, which sporadically discharges pus. The lesion persists with no tendency to spontaneous regression. Histopathologically, it consists of elaborate, epithelialized galleries connected to the skin surface at multiple points. It contains corneocytes, hairs, bacteria, serum, inflammatory cells and epitheloid granulomas. A surgical thread placed into the skin provides a model in which the generation of sinus tracts can be studied. Therapy is difficult. Intralesional corticosteroid injection, cryosurgery and isotretinoin are not always very effective. Sometimes complete excision of the lesion is necessary. The draining sinus is a special form of scar analogous to the pilonidal cyst.