CONCISE REPORT Efficacy of etanercept for treatment of Crohn’s related spondyloarthritis but not colitis

The seronegative spondyloarthropathies (SpAs) are associ-ated both with clinical and subclinical colitis. Recently bio-logical blockade with the tumour necrosis factor alpha (TNFα) antagonists infliximab and etanercept has been shown to be effective in the treatment of SpA. However, only infliximab is efficacious in the treatment of colitis in patients with Crohn’s SpA. We report on two patients with SpA and associated Crohn’s disease treated with etanercept whose arthritis showed an excellent response with complete resolution of spinal pathology, whereas their Crohn’s disease persisted or flared. These findings suggest that the effect of TNFα blockade in SpA differs between the joint and the bowel. The spondyloarthropathies (SpAs) are a heterogeneousgroup of HLA-B27 associated arthropathies characterisedby joint inflammation with enthesitis and an association with low grade colitis that is reminiscent of Crohn’s disease.1 Historically the therapeutic options in SpA have been limited, but recent studies have shown that biological blockade with the tumour necrosis factor α (TNFα) antagonists infliximab and etanercept is efficacious in ankylosing spondylitis2 3 and psoriatic arthritis.4 5 We have previously shown that etanercept had good clinical efficacy in patients with resistant SpA.6 As both infliximab and etanercept remove excess TNFα it seems likely that both drugs have similar mechanisms of action in SpA. However, it appears that only infliximab but not etaner-cept is efficacious in Crohn’s disease that is associated with SpA-type arthropathies. This suggests that there may be differences in the pathogenesis of the bowel disease and joint pathology in SpA. Here we report on two patients in whom etanercept was very effective for arthritis but not for Crohn’s disease, suggesting that the principal mechanism of action of TNFα blockade is within the joints