Azathioprine induced colitis: a case report and review of the literature.

We report a case of an allergic hypersensitivity reaction on azathioprine presenting with colitis. Allergic reactions on azathioprine are common in patient with inflammatory bowel disease. The clinic of the allergic reaction on azathioprine in our patient was atypical in the way it mimicked an acute exacerbation of inflammatory bowel disease. The pathogenesis of the allergic reaction is still unclear. Although re-challenge can be life-threatening and should always be done with precautions, it may definitively proof the causal association with the drug and decide for definitive cessation In allergic reactions there is no link with TPMT activity but other genetically predispositions are proposed.