New rheumatoid arthritis genetic factor and C5 serum level

There is a significant body of evidence suggesting that complement activation plays an important role in the maintenance of the polyarticular chronic synovitis characteristic of rheumatoid arthritis (RA).1 Recently, a novel RA genetic risk factor was described, involving allelic polymorphisms on the chromosome 9, in the intergenic region between complement factor 5 ( C5 ) and tumour necrosis factor receptor-associated factor 1 ( TRAF1 ) genes.2,3,4 The new genetic factor, detected in RA case-control studies for anti-cyclic citrullinated peptide antibodies and/or rheumatoid factor positive (RF+) RA in North American, Swedish and Dutch populations,2,3 was confirmed by linkage in a …