A case of acute renal failure of multiple myeloma due to monoclonal type I cryoglobulinemia with thrombotic microangiopathy.

The term cryoglobulinemia (CG) is used to refer to vasculitis due to so-called mixed cryoglobulins containing immune complexes. Although most cases of monoclonal CG, called type I CG, are asymptomatic, purpura, skin ulcers, and renal failure develop in some cases. Hematological disorders are the underlying diseases in most cases, on which the therapeutic strategies available and the prognosis of patients depends. We here report a case of a 47-year-old man who had pain in both his ankles, with palpable purpura and epistaxis, and presented with acute renal failure. Monoclonal immunoglobulin (Ig) G-κ protein was detected and cryoglobulin was also positive. Renal biopsy revealed emboli with a fibrillar structure in the glomeruli and renal tubule lumina. The complication of thrombotic microangiopathy (TMA) occurred during the course. Therefore, plasma exchange and hemodialysis were added to methylprednisolone pulse therapy. The treatment was successful, dissipating the purpura. However, the purpura relapsed and renal dysfunction progressed when the administration of oral steroids was tapered. Bone marrow biopsy was performed again, which indicated an increase in abnormal plasma cells. The patient was finally diagnosed as multiple myeloma. Then, bortezomib-dexamethasone therapy was initiated. This is the first case of type I CG with monoclonal IgG complicated by TMA during the course; it provides insight into the pathogenesis of renal dysfunction associated with type I CG.