Reactive perforating collagenosis, characterized by extrusion of collagen fibers through the epidermis, usually begins in infancy or childhood and appears clinically as recurrent umbilicated papules that resolve spontaneously in 6 to 8 weeks (summary by Trattner et al., ... Reactive perforating collagenosis, characterized by extrusion of collagen fibers through the epidermis, usually begins in infancy or childhood and appears clinically as recurrent umbilicated papules that resolve spontaneously in 6 to 8 weeks (summary by Trattner et al., 1991). The disorder was first described by Mehregan et al. (1967). Kanan (1974) described 2 unrelated consanguineous families in which 7 adults showed this lesion. Superficial trauma seemed to be a triggering factor in most of the lesions. Cold weather aggravated them. Onset was in early childhood in most. Poliak et al. (1982) described this lesion in black and Hispanic patients with diabetes and renal failure requiring dialysis. The condition must be distinguished from elastosis perforans serpiginosa (130100) and Kyrle disease (149500). Trattner et al. (1991) described brothers with this disorder. In addition to lesions in sun-exposed areas of the face, arms, and legs beginning since the age of 3, one of them had, at age 22, lesions of the lips and oral cavity. Trattner et al. (1991) believed that this was the first report of mucosal involvement in RPC.