Pretibial pruritic papular dermatitis: A distinctive cutaneous manifestation in response to chronic rubbing.

We describe the clinico-pathologic features of 44 patients with a peculiar pretibial pruritic papular dermatitis (PPPD). Clinically, PPPD consists of discrete, roundish, extremely pruritic papules with a smooth surface caused by the delicate and persistent rubbing of pretibial skin. Histologically, PPPD showed minimal compact orthokeratosis, flattening of the rete ridges, a superficial and mid-dermal perivascular and interstitial infiltrate of lymphocytes, histiocytes, eosinophils and multinucleated fibroblasts, and thickened collagen bundles in haphazard array in the superficial dermis. The clinical picture of PPPD closely resembled that of lichen simplex chronicus/circumscribed neurodermatitis or lichen amyloidosus. Histologically, the absence of uneven psoriasiform epidermal hyperplasia, marked compact orthokeratosis, hypergranulosis, and coarse bundles of collagen arranged in vertical streaks in the papillary dermis distinguished PPPD from lichen simplex chronicus, whereas the lack of amyloid deposits in the dermal papillae differentiated PPPD from lichen amyloidosus. We suggest that PPPD is an unusual morphologic expression of gentle and chronic rubbing of pretibial skin with distinctive histopathologic features.