Early environmental factors and rheumatoid arthritis.

The precise cause of autoimmune diseases such as rheumatoid arthritis (RA) remains uncertain. In recent years there has been extensive investment in pursuing genes important in RA. However, estimates suggest that the risk of developing RA is at most 50% determined by genes. There has been limited success defining the environmental factors important in developing RA. We hypothesize that this lack of success may be due to a concentration on the time around disease onset. There is evidence of production of the autoantibodies rheumatoid factor (RF) and anti-cyclic citrullinated peptides (anti-CCP) and increased levels of C-reactive protein (CRP) years before RA becomes clinically apparent. In addition, early life events including intrauterine growth retardation (IUGR) may have long lasting effects on immune function. We review the evidence that the early environment through effects on growth and infectious exposure may influence the likelihood of developing autoimmune diseases such as RA.