A 69-year-old woman presented with bilateral digital necrosis, which had developed over a period of 2 months (Panels A and B). One year earlier, new-onset Sjögren's syndrome and painful Raynaud's phenomenon had developed. Nifedipine and topical nitroglycerin failed to improve symptoms. The patient did not smoke. Her family history was notable for Waldenström's macroglobulinemia. Laboratory studies were positive for cryoglobulins, and serum protein electrophoresis with the use of immunofixation revealed a monoclonal IgM spike at 345 mg per deciliter with kappa light-chain restriction. Tests for hepatitis C virus, serum viscosity, and lymphocyte counts were normal. The patient received a diagnosis of cryoglobulinemia with an IgM monoclonal gammopathy of unknown significance. To treat the cryoglobulinemia, two courses of chemotherapy with dexamethasone, cyclophosphamide, and rituximab were administered over a period of 2 weeks. After 1 month without clinical improvement, video-assisted thoracic sympathectomy was performed to increase perfusion. After the sympathectomy, the patient's hands became warm and moist. One year after presentation, cryoglobulins were undetectable, the patient's fingers had gradually improved, and there had been no amputations.