Acquired Perforating Dermatosis: Comparison of an Acquired Perforating Dermatosis and Perforation as an Incidental Histologic Finding

Abstract A 66‐year‐old Japanese woman with a rare acquired perforating disorder, usually called adult‐type reactive perforating collagenosis, is reported. The patient had poorly controlled diabetes mellitus with retinopathy under oral diabetic medication. She was found to have multiple papules and umbilicated nodules on the trunk and four extremities when she was admitted and examined for the origin of jaundice and severe pruritus of sudden onset. In the biopsy specimen, collagen fibers were observed to be eliminated from the dermis through epidermal tunnel‐like perforations. No elastic fibers were eliminated, and serial sectioning of the specimen could not prove follicular perforation. Adenocarcinoma of the biliary duct was found to be the cause of the jaundice with pruritus. Although such cases are usually classified as acquired reactive perforating collagenosis of adult onset, proposed reclassification for acquired perforating disorders is discussed. Another case which also showed perforation and transepithelial elimination of both collagen and elastic fibers as an incidental histologic finding is described. Such elimination seems to be a not uncommon step in the formation of pruriginous eruptions. Therefore, these cases should be differentiated from acquired‐type characteristic perforating disorders.