Levamisole-Adulterated Cocaine-Associated Vasculopathy in a 73-Year-Old Woman: Diagnostic Challenges in Primary Care.

Levamisole, a common cocaine adulterant, can cause a distinctive skin disease combining non-inflammatory microvascular occlusion (vasculopathy) with inflammatory vessel-wall injury (vasculitis), marked by retiform purpura, skin necrosis, and atypical antineutrophil cytoplasmic antibody (ANCA) patterns. The condition is frequently misdiagnosed as primary ANCA-associated vasculitis, exposing patients to unnecessary immunosuppression. This study aimed to describe a probable case of levamisole-associated vasculopathy in an older adult diagnosed in primary care and to highlight nonjudgmental substance-use screening in geriatric patients. A 73-year-old woman with tobacco and cocaine use disorder presented to a family medicine clinic with progressive bilateral lower-extremity retiform purpura. She reported using cocaine by sprinkling it onto marijuana. Serologic workup showed negative antinuclear antibody, negative ANCA by indirect immunofluorescence, and negative myeloperoxidase antibodies, with an elevated proteinase-3 antibody (85 AU/mL; reference range: <19 AU/mL). Chest computed tomography showed no pulmonary involvement, and a skin biopsy was not performed. In the absence of skin biopsy, levamisole assay, or urine toxicology during the active presentation, the clinical picture, serologic pattern, and substance-use history supported a probable diagnosis of cocaine-associated vasculopathy of presumed levamisole origin rather than primary ANCA-associated vasculitis. Levamisole exposure was not confirmed by analysis of the substance used or by assay of a clinical specimen. Management included cocaine cessation counseling, topical corticosteroids, and rheumatology referral, and the lesions resolved completely within two months of cocaine cessation. We did not find a previously published case of levamisole-associated vasculopathy diagnosed in an older adult in a primary care setting, a combination that appears to be rarely, if ever, reported. The diagnosis was probable rather than confirmed, since neither histopathology nor direct levamisole testing was available. Awareness of this presentation may reduce diagnostic error, avoid unnecessary immunosuppression, and reinforce the value of nonjudgmental substance-use assessment in older adults.