There is a strong and likely causal association between chronic hepatitis C virus (HCV) infection and glomerular disease [1,2]. Several types of renal disease have been recognized including mixed cryoglobulinemia, membranoproliferative glomerulonephritis (MPGN), membranous nephropathy [3-9], and polyarteritis nodosa. Crescentic glomerulonephritis may be superimposed on any of these glomerular lesions.
Less commonly, other glomerular lesions have been reported in HCV-infected patients, including focal segmental glomerular sclerosis [10-12], proliferative glomerulonephritis [13-15], and fibrillary [16-18] and immunotactoid glomerulopathies . In some patients, glomerular disease may be clinically silent [19,20]. (See 'Clinically silent glomerular disease' below.)
Glomerular diseases can occur both in native kidneys and renal allografts. A renal thrombotic microangiopathy and an atypical variant of acute cellular rejection have been associated with HCV infection in renal transplant recipients. Acute and chronic transplant glomerulopathy also have been described [10,21]. It remains unclear, however, why only some patients with HCV infection develop these complications. (See "Renal disease associated with hepatitis C virus after renal transplantation".)
This topic provides an overview of the renal diseases associated with chronic HCV infection and the approach and response to therapy. The diagnosis and management of HCV infection and of HCV-associated renal disease following renal transplantation are discussed separately. (See "Overview of the management of chronic hepatitis C virus infection" and "Renal disease associated with hepatitis C virus after renal transplantation" and "Treatment regimens for chronic hepatitis C virus genotype 1" and "Treatment regimens for chronic hepatitis C virus genotypes 2 and 3" and "Diagnosis and evaluation of chronic hepatitis C virus infection".)
MIXED (IgG/IgM) CRYOGLOBULINEMIA
Mixed cryoglobulinemia is a systemic vasculitis. Affected patients typically present with nonspecific systemic symptoms, palpable purpura, arthralgias, fever, renal disease, neuropathy, hypocomplementemia (C4<C3), and other manifestations . The clinical manifestations of the renal disease may include hematuria, nephritic range proteinuria, and renal insufficiency. Fifty percent of patients have moderate renal insufficiency, and hypertension is present in 80 percent of patients [23,24]. In general, the renal prognosis is good . However, renal disease is the primary cause of morbidity and mortality in patients with mixed cryoglobulinemia . Laboratory studies indicate the presence of circulating cryoglobulins, which are most commonly type II cryoglobulins in which the rheumatoid factor (or antibody that is directed against the Fc portion of IgG) is a monoclonal IgM kappa. The complement components, C3, C4, and C1q, are usually low. (See "Clinical manifestations and diagnosis of the mixed cryoglobulinemia syndrome (essential mixed cryoglobulinemia)" and "Clinical manifestations and diagnosis of the mixed cryoglobulinemia syndrome (essential mixed cryoglobulinemia)", section on 'Clinical manifestations'.)