In the 67 patients with polyarthritis, patients in the low MBL2 genotype group were younger (4.4 years, IQR 3.6 to 7.0 years) at onset of disease than the patients in the medium (10.1 years, IQR 8.4 to 13.0 years) and high (9.5, IQR 5.6 to 13.0 years) genotype groups (P = 0.05; Table 3). This evidence concerns the gene MBL2 and polyarticular arthritis.