Cutaneous manifestations of antineutrophil cytoplasmic antibody-associated vasculitis (AAV): a concise review with emphasis on clinical and histopathologic correlation.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) comprises a group of small vessel vasculitides grouped by commonalities of clinical manifestations and ANCA testing. Skin findings are not uncommon, although there is considerable overlap and many times nonspecificity. In general, patients with skin findings tend to have more significant systemic illness, and skin lesions most often develop simultaneously or following onset of systemic symptoms. There are clinical and pathological clues of help in the differentiation of skin findings in these disorders. Purpura of various forms with leukocytoclastic vasculitis is common to all AAV. Granulomatosis with polyangiitis (GPA) comprises the largest number of patients with an AAV. Upper airway, oral, ear, and facial lesions, with or without granuloma, are more commonly seen in this AAV. Pyoderma gangrenosum-like lesions, including facial location, while not common are most closely associated with GPA. Eosinophilic granulomatosis with polyangiitis (EGPA) as its name implies is more closely associated with eosinophilic, allergic, or asthmatic conditions. Papular lesions of the extensor extremities showing extravascular granulomatous changes are characteristic but not specific for EGPA. Microscopic polyangiitis (MPA) is more closely associated with livedoid skin changes, and vascular inflammation tends to be deeper in the skin than with the other AAV. Extravascular granulomas are not expected. While the skin findings in AAV can be nonspecific and overlapping, combining careful full skin examination with histopathologic study of selected lesions is critical to making the correct diagnosis and in ruling out other similar diseases not ANCA related. The aim of this article is to encourage increased participation by dermatologists and dermatopathologists in the care of these patients.