Acrally distributed dermatoses: Vascular dermatoses (purpura and vasculitis).

Purpuric lesions appear in acral distribution in a variety of conditions and often provide clues to the clinical diagnosis. Purpuric means "hemorrhagic"-that is, the lesions do not blanch from pressure. This review focuses on dermatoses that produce hemorrhagic lesions in acral distribution from the large groups of the vasculitic diseases and their mimics. Cutaneous small vessel vasculitis is confined to the skin, involves mainly postcapillary venules, and has the hallmark manifestation of palpable purpura. Henoch-Schönlein purpura is an immune complex-mediated systemic vasculitis of the small vessels with manifestations from the skin, joints, kidneys, and gastrointestinal system. Only cases where the immune complexes contain immunoglobulin A type are classified as Henoch-Schönlein purpura. Cryoglobulinemic vasculitis is induced by the deposition of cold-precipitated immune complexes in the small vessels. Urticarial vasculitis comprises a spectrum of conditions with the characteristic course of chronic urticaria, with wheals that persist longer than 24 hours, leave hyperpigmentation, and have leukocytoclastic vasculitis on histologic examination. Polyarteritis nodosa is a rare multisystem, segmental necrotizing vasculitis of mainly the medium-sized vessels. Pigmented purpuric dermatoses are chronic benign dermatoses characterized by petechiae, purpura, and increased skin pigmentation. The hallmark of pigmented purpuric dermatoses is their orange-brown, speckled, cayenne pepper-like discoloration.