BACKGROUND: Extrahepatic manifestations associated with Hepatitis C virus (HCV) such as arthritis, vasculitis, cryoglobulinemia, are well known. However, HCV related arthritis in the absence of clinical, biochemical and histological evidence of liver disease is not common. This article deals with such a case and its response to interferon therapy. CASE REPORT: We present a case of a 32 year old Filipino male who presented with bilateral symmetrical painful swelling of multiple joints including, hands, elbows, shoulders, and knees. Serum rheumatoid factor, antinuclear antibodies and a comprehensive work-up for rheumatologic disorders were all negative. Both initially and subsequently, serological tests for hepatitis A, B, and autoimmune liver diseases, Wilson's disease, hemochromatosis, syphilis, human immunodeficiency virus (HIV) and cryoglobulinemia were negative, initially and subsequently. However, the hepatitis C antibody test was positive and hepatitis C viral RNA was detected in high titers. The joint symptoms did not improve despite therapy with nonsteroidal anti-inflammatory drugs and a short course of prednisone prescribed earlier by his primary care physician. The patient then requested and was subsequently treated with interferon alpha 2b. RESULTS: The patient responded rapidly to the interferon therapy with significant and sustained improvement in joint symptoms and disappearance of hepatitis C viral RNA from his serum. CONCLUSIONS: HCV arthritis should be considered in the differential diagnosis of seronegative arthritis of undetermined etiology even in the setting of normal liver chemistries.

Keywords: Anti-Inflammatory Agents, Non-Steroidal - therapeutic use, Antiviral Agents - therapeutic use, Arthralgia - etiology, Arthritis, Infectious - virology, Hepatitis C - drug therapy, Interferon-alpha - therapeutic use, RNA, Viral - blood, Recombinant Proteins