Reactive perforating collagenosis (RPC) is a type of perforating disorder that is characterized by transdermal elimination of collagen fibers. There are two forms of RPC. The most common form is acquired RPC, which is generally observed in patients with chronic kidney disease and diabetes mellitus. Acquired RPC can rarely occur in the setting of medications or malignancies. Like other members of the acquired perforating dermatosis group, the lesions generally occur only on the legs or in a generalized distribution.

There is also a familial form of RPC, which has an onset in childhood. Familial RPC can persist throughout childhood and into adulthood, and generally presents on the hands and upper extremities. Lesions are induced by trauma.

The pathogenesis is unknown, but the familial disease is generally thought to be inherited in an autosomal recessive manner (although an autosomal dominant pattern has been observed in some families). Males and females are equally affected, and lesions generally start within the first few years of life in the inherited form.

The primary lesion is a skin-colored papule 1-3 mm in diameter that reaches a maximum size of about 6 mm within a month; 6-8 weeks later, it regresses spontaneously (often leaving temporary areas of hypopigmentation behind or slight scarring). There is a central keratotic plug seen in more advanced lesions that is firmly adherent and, if removed, results in bleeding. Koebner phenomenon may occur, resulting in new lesions that are often linearly arranged. Pruritus is often severe. There are often periods of disease remission and exacerbation.