Synonym: reactive perforating collagenosis
Clinical features:
(1) The patient is typically a middle-aged adult, often with one or more predisposing conditions (see previous section).
(2) The patient develops multiple, umbilicated keratotic papules.
(3) The papules are often pruritic.
(4) The papules may be occur in a linear pattern.
(5) The lesions are more common on extensor surfaces of the extremities and the trunk.
(6) The lesions resolve slowly, leaving small scars or small areas of discoloration.
(7) The lesions may disappear only to reappear months to years later.
(8) If the patient scratches the lesions then secondary infection or scarring may occur.
Pathologic features:
(1) The epidermis shows invaginations, in which there are multiple perforations.
(2) Early lesions show an intense inflammatory response at the site of a perforation and extending into the adjacent dermis. Later a chronic inflammatory cell infiltrate with foreign-body type giant cells develops.
(3) A fully developed lesion shows deposits of degenerated collagen and elastic fibers, irregular acanthosis and dome-shaped hyperkeratosis.
