There may be a connection between the two conditions but what the link is remains unknown. HCV may heighten the body's immune response. Since rheumatoid arthritis is an autoimmune disease (the body attacking itself), it's possible the immune system is TOO stimulated to fight the HCV and ends up fighting itself.

A second theory is related to the drug treatment for HCV with interferon. The hepatitis C virus (HCV) often causes chronic liver disease. Since the liver metabolizes drugs taken, a damaged liver may result in improper drug use and elimination by the body. This may be why interferon triggers RA in some people.

The main problem in having both diseases is the impact on the liver. Patients with HCV aren't always able to take advantage of the newer drugs for RA. Some of the medications used to treat the rheumatoid arthritis (RA) are known to damage the liver even more. Drugs to help manage the hepatitis can make the RA worse. Lab tests for liver function are needed more often to watch for developing problems.