Multiple Myeloma: A Forgotten Imitator of Anti-Neutrophil Cytoplasmic Antibody (ANCA) Vasculitis.

Leukocytoclastic vasculitis is a neutrophilic angiitis with diverse etiologies, including both inflammatory and neoplastic conditions, such as anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) and multiple myeloma (MM). Skin involvement in MM is rare, occurring in less than 1% of cases. We present a case of a patient with retiform purpura and peripheral neuropathy in the lower limbs, secondary to IgG lambda MM, which mimicked AAV. Skin manifestations in MM can appear as the initial symptom or at any stage of the disease. This case highlights the critical role of protein electrophoresis in the initial evaluation of patients with systemic inflammatory conditions.