Multiple Myeloma-Associated Leukocytoclastic Vasculitis Mimicking Autoimmune Vasculitis

A 52-year-old man was admitted because of complaints of swelling and skin rashes on the extremities, fever, and arthralgia. Physical examination revealed bilateral ankle and wrist joint tenderness and livedo racemosa and purpura on the lower extremities (Figure, A). Cutaneous lesion biopsy showed leukocytoclastic vasculitis (Figure, B). Laboratory testing revealed a hemoglobin level of 5.6 g/dL, mildly decreased glomerular filtration rate, and an immunoglobulin G level of 3,936 mg/dL. Serum and urine immunofixation electrophoresis showed monoclonal kappa light chains. Bone marrow biopsy revealed proliferation of monoclonal plasma cells (Figure, C). Finally, the patient was diagnosed with leukocytoclastic vasculitis as the initial presentation of multiple myeloma. Cutaneous symptoms resolved within 6 weeks following treatment with daratumumab, lenalidomide, and dexamethasone (Figure, D). Although leukocytoclastic vasculitis is commonly associated with immune-mediated systemic vasculitis, cutaneous leukocytoclastic vasculitis may be observed in case of malignancy. Monoclonal gammopathies should be considered in cases of leukocytoclastic vasculitis associated with renal and blood disorders.Differential diagnosis: immunoglobulin A vasculitis, microscopic polyarteritis, granulomatosis with polyangiitis, and eosinophilic granulomatosis with polyangiitis.