A 38-year-old woman has had malaise and arthralgias for the past 14 months. On physical examination, she has scleral icterus and 1- to 3-cm areas of reddish-purple discoloration on her skin. Several of these areas show focal ulceration. Laboratory findings show total protein, 7.1 g/dL; albumin, 3.3 g/dL; AST, 127 U/L; ALT, 145 U/L; alkaline phosphatase, 80 U/L; total bilirubin, 4 mg/dL; and direct bilirubin, 3.1 mg/dL. Serologic test results are positive for anti-HCV and negative for anti-HBs and IgM anti-HAV. Urinalysis shows 4+ proteinuria and 1+ hematuria. CT scan of the abdomen shows a small amount of ascites, mild hepatomegaly, and no splenomegaly or lymphadenopathy. A biopsy specimen of an ulcerated skin lesion shows leukocytoclastic vasculitis involving the upper dermis. What is the most likely diagnosis?

Patients with hepatitis C infection can develop chronic hepatitis with persistently elevated liver enzymes. Some patients with hepatitis C develop a mixed cryoglobulinemia with a polyclonal increase in IgG. Renal involvement is common, with either nephrotic or nephritic features. Cryoglobulinemic vasculitis leads to skin hemorrhages and ulceration. Autoimmune hemolytic anemia can lead to a predominantly indirect hyperbilirubinemia. Although hepatocellular carcinoma may complicate hepatitis C infection, a mass lesion would be seen on CT scan, and the alkaline phosphatase level usually is elevated when an intrahepatic mass is present. Chronic liver disease may complicate hereditary hemochromatosis, but these patients usually do not have hepatitis C, and the skin has a slate color, not purpura. Multiple myeloma can increase the serum globulin and produce renal disease, but hepatitis is usually not part of myeloma; vasculitis likewise is not part of myeloma.