The TRAF1/C5 region is a risk factor for polyarthritis in juvenile idiopathic arthritis

Background

Juvenile idiopathic arthritis (JIA) is a chronic disorder in which both genetic and environmental factors are involved. Recently we identified the TRAF1/C5 region (located on chromosome 9q33-34) as a risk factor for rheumatoid arthritis (RA) (p_combined = 1.4 × 10^-8) [1]. In the present study the association of the TRAF1/C5 region with the susceptibility to JIA was investigated.

Methods

A case-control association study was performed in 338 Caucasian JIA patients and 511 healthy individuals. We genotyped SNP rs10818488 as a marker for the TRAF1/C5 region.

Results

The A-allele was associated with the susceptibility to Rheumatoid Factor (RF) negative polyarthritis with an 11% increase in allele frequency (OR 1.54, 95% CI 1.09–2.18; p = 0.012). This association was stronger when combining subtypes with a polyarticular phenotype (OR 1.46, 95% CI 1.12–1.90; p = 0.004). In addition, we observed a trend towards an increase in A-allele frequency in patients with extended oligoarthritis versus persistent oligoarthritis (49% and 38% respectively); p = 0.055.

Conclusion

Apart from being a well replicated risk factor for RA, TRAF1/C5 also appears to be a risk factor for the RF negative polyarthritis subtype of JIA and, more generally, seems to be associated with subtypes of JIA characterized by a polyarticular course.