Generalized perforating granuloma annulare.

Generalized perforating granuloma annulare is characterized by 1 to 4 mm umbilicated papules on the extremities, and is most commonly seen in children and young adults. Transepithelial elimination of mucinous, degenerating collagen fibers and surrounding palisading lymphohistiocytic granulomas are important histologic features. Perforating sarcoidosis and perforating granuloma annulare may be difficult to differentiate because of a similar clinical appearance and the presence of sarcoidal granulomas in biopsy specimens. A particularly high incidence of perforating granuloma annulare has been reported in the Hawaiian Islands.