Ulcerative colitis is often accompanied by the development of extraintestinal, mainly articular, manifestations. Genetic differences could be underlying that clinical heterogeneity. We performed a case-control study to determine whether TNFab microsatellites or HLA-DR alleles were associated with the development of articular manifestations in patients with ulcerative colitis. With that aim, a total of 84 ulcerative colitis patients with articular manifestations and 172 without them were genotyped for TNFab microsatellites and HLA-DR. A healthy control sample (n = 595) was also included for comparative purposes. Haplotypes were inferred with the Arlequin software. The influence of HLA-DRB1*0103 and HLA-B27, factors previously known to be associated with extraintestinal manifestations, was specifically addressed. We observed that TNFa6b5 minihaplotype increases the susceptibility to developing articular manifestations in ulcerative colitis patients (p = 0.003, OR = 2.39). The locus HLA-DR does not appear to be involved in these extraintestinal manifestations by itself; however, the frequency of subjects carrying TNFa6b5 in combination with DR1, DR7, or DR11 is very significantly increased in patients with articular manifestations (p = 3.9 x 10(-8)). The associations found were independent of DRB1*0103 and HLA-B27. Thus, it seems that the development of articular manifestations in ulcerative colitis patients appears to be influenced by some genetic factor(s) present in some major histocompatibility complex haplotypes.