Reactive perforating collagenosis is a rare, familial, nonpuritic skin disorder characterized by papules that grow in a diameter of 4 to 6mm and develop a central area of umbilication to which keratinous material is lodged.

Keratotic papules measuring 1 to 6 mm develop on the extensor surface of the hands, the elbows, and the knees following superficial trauma.

They appear as pin-sized lesions that grow to a papule of about 6mm in the following 3–5 weeks.

They undergo spontaneous resolution in about 6–8 weeks leaving residual scarring.

[3] In this form, keratotic papules develop on the trunk and extremities.