[A case of MPO-ANCA-related microscopic polyangiitis with mixed cryoglobulinemia]

A 49-year-old woman with a history of chronic hepatitis C virus infection and Hashimoto disease was admitted to our hospital because of proteinuria, hematuria, purpura, and edema in the lower extremities. Laboratory data on admission revealed proteinuria (0.2 g/day), microscopic hematuria (3+) with RBC casts, renal dysfunction(serum creatinine 1.4 mg/dl), positive anti nuclear antigen (x640, speckled type), hypocoplementemia, mixed cryoglobulinemia (type III), and hepatitis C virus infection (AST 45 IU/l, ALT 33 IU/l). MPO-ANCA level was found to be high (356 EU). In renal biopsy, most glomeruli showed crescentic formation with the weak deposition of IgG, IgM, and C3 in the mesangial area and along the capillary wall. She was diagnosed as having systemic vasculitis associated with MPO ANCA. Methylprednisolone pulse therapy followed by oral prednisolone (40 mg/day) effectively normalized MPO ANCA level. It has been reported that ANCA is found in patients with HCV-associated mixed cryoglobulinemia. Therefore, in chronic hepatitis C patients with systemic vasculitis, we should consider the possibility of ANCA-related microscopic polyangiitis and make a correct diagnosis by renal biopsy.