Cutaneous manifestations of hyperviscosity syndrome in relapsed immunoglobulin A multiple myeloma: A case report

Hyperviscosity syndrome is uncommon in immunoglobulin A (IgA) multiple myeloma and rarely presents with prominent cutaneous manifestations. We describe a 73-year-old woman with relapsed IgA myeloma admitted with encephalopathy, blurred vision, livedo reticularis, hemorrhagic crusts, and distal fingertip necrosis. Serum IgA peaked at 3524 mg/dL; peripheral smear showed intense rouleaux and circulating plasma cells. Viscometry and fundoscopy were unavailable. Empirical therapeutic plasma exchange under American Society for Apheresis Category I led to neurological recovery after the third session, regression of cutaneous lesions, and a 78% reduction in IgA. Cutaneous findings can be the dominant diagnostic clue.