Pseudoperforation: An uncommon histologic phenomenon in prurigo misleading for the diagnosis of reactive perforating collagenosis

Prurigo is a common skin condition characterized by vigorous scratching. Although ulceration is not uncommon in prurigo, a perforating-like lesion was not previously reported. In this study we described series of cases of prurigo with perforating-like lesions and discussed its relation to acquired perforating dermatoses. The study included 32 cases, during the period from 2008 to 2013. Clinical data and histological features were recorded and analyzed. The study included 78.1% males and 21.9% females with a mean age of 39.3 ± 5.61 years. History of insect bite was evident in 28.1%, hepatitis C virus infection in 46.9%, and diabetes mellitus in 9.4% of patients. Histologically, well developed lesions showed full thickness epidermal degeneration overlay by a cup-shaped crater. The contents of the crater included collagen and elastic fibers, bacterial colonies, inflammatory cells and necrotic keratin. The dermis showed non-altered collagen, increased vascularity and mixed inflammatory infiltrate. We believe that this pseudoperforation process is a secondary response to vigorous scratching in prurigo patients and not a primary mechanism as occurred in perforating dermatoses. The absence of altered collagen, the presence of full thickness epidermal necrosis and concomitant elimination of elastic fibers are significant histologic clues for differentiation between both conditions.