Hepatitis C virus infection mimicking systemic lupus erythematosus: study of hepatitis C virus infection in a series of 134 Spanish patients with systemic lupus erythematosus.

OBJECTIVE: To determine the prevalence and clinical significance of hepatitis C virus (HCV) infection in patients with systemic lupus erythematosus (SLE).
METHODS: We investigated 134 consecutive SLE patients (121 women and 13 men; mean age 35 years) who fulfilled the 1982 revised criteria for SLE of the American College of Rheumatology. Two hundred consecutive volunteer blood donors were also studied. Serum from all patients and controls was tested for antibodies to HCV (by third generation enzyme-linked immunosorbent assay and confirmed by third generation recombinant immunoblot assay [RIBA-3]).
RESULTS: Antibodies to HCV were present in 18 patients with SLE (13%) and in 2 (1%) of the blood donors studied. Among the anti-HCV-positive group, HCV infection was confirmed (by RIBA-3 and polymerase chain reaction) in 15 SLE patients (11%) and in the 2 blood donors (1%) (P < 0.001). We observed a lower frequency of cutaneous SLE features (40% versus 76%; P = 0.01) and positivity for anti-double-stranded DNA (anti-dsDNA) (33% versus 81%; P < 0.001), and a higher frequency of hepatic involvement (93% versus 2%; P < 0.001), low C4 levels (73% versus 39%; P = 0.002), low CH50 levels (73% versus 44%; P = 0.03), and cryoglobulins (60% versus 22%; P = 0.02) in SLE patients with HCV infection compared with SLE patients without infection.
CONCLUSION: The prevalence of HCV infection in SLE patients was higher than in blood donors from the same geographic area. SLE HCV-positive patients showed a lower frequency of cutaneous SLE features and anti-dsDNA antibodies, and a higher prevalence of liver involvement, hypocomplementemia, and cryoglobulinemia. HCV testing should be considered in the diagnosis of SLE, especially in patients who lack the typical cutaneous features of SLE or who have low titers of autoantibodies, cryoglobulinemia, or liver involvement.