A 46-year-old man simultaneously developed chronic seronegative non de
structive oligoarthritis and chronic watery diarrhoea. Biopsies from t
he colorectal mucosa showed a thickened subepithelial collagen layer c
onsistent with collagenous colitis. Collagenous colitis should be adde
d to the list of causes of enteropathic arthritis.