Exposure to levamisole, a prevalent adulterant of illicit cocaine in North America, can induce a distinctive clinical syndrome of retiform purpura and cutaneous necrosis affecting the extremities, ears, and skin overlying the zygomatic arch. Biopsies reveal widespread thrombosis of small cutaneous vessels with varying degrees of vasculitis. The syndrome is associated with the lupus anticoagulant, IgM antibodies to cardiolipin, and very high titers of p-ANCAs (due to autoantibodies to elastase, lactoferrin, cathepsin-G, and other neutrophil components rather than to myeloperoxidase alone). There is no consensus on treatment of levamisole-induced purpura, but early lesions can resolve with abstinence. Use of levamisole-adulterated cocaine also has been linked to neutropenia, agranulocytosis, and pauci-immune glomerulonephritis.
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et al. Demographic, clinical, and immunologic correlates among a cohort of 50 cocaine users demonstrating antineutrophil cytoplasmic antibodies. J Rheumatol. 2019 Sep;46(9):1151–6.