Background Treatment with bortezomib is frequently associated with haematological toxicity. In addition infrequent gastrointestinal disorders such as ischaemic colitis, irritable bowel syndrome and paralytic ileus are described, among others.

Purpose To describe a case of ischemic colitis associated with treatment with bortezomib and to evaluate causality.

Materials and methods The authors report on a woman, 77 years old, diagnosed with multiple myeloma, chronic renal insufficiency and echinococcosis, being treated with enalapril 20 mg/day, bisoprolol 2.5 mg/day, isosorbide 50 mg/day, calcium carbonate 1.25 g/8 h, furosemide 40 mg/day, darbepoetin α 40 mcg/15 days, omeprazole 20 mg/day. In June 2011, she was given fresh treatment with bortezomib 2.2 mg/72 h and dexamethasone 40 mg/week. After the fourth dose, the patient went to the emergency services with abdominal pain and constipation that had been coming on for several days. It was decided to interrupt treatment and she was admitted to the digestion ward. Naranjo's algorithm and Karch–Lasagna's algorithm were used to determine the reason.

Results An urgent colonoscopy showed abundant red stained faecal residue in the descending colon, diffuse mucous with black plaques and surface ulcers which demonstrated severe ischaemic colitis. An abdominal axial CT scan reflected a remarkable oedematous thickening of the colon wall (7 cm) with adjacent frayed fatty tissue related to the colitis diagnosis. After 12 days the patient progressed satisfactorily on conservative treatment having interrupted her standard treatment. When the bortezomib treatment restarted the patient resumed the same medical regimen but very soon she experienced abdominal distension, nausea and vomited bile. Chronic mesenteric ischaemia was diagnosed. After a further 15 days the patient was discharged from hospital and is now trying oral lenalidomide as second line treatment of the multiple myeloma. After applying the causality algorithms, the adverse reaction came out in both cases as definitively due to bortezomib (10 points).

Conclusions Ischaemic colitis is described in the bortezomib technical data sheet as an uncommon adverse event (<0.01%) as reported in postmarketing studies. In the Sistema Español de Farmacovigilancia (FEDRA) Spanish Pharmacovigilance System for Medicines for Human Use 239 bortezomib adverse events are recorded, 44 related to gastrointestinal disorders. Close monitoring of patients showing constipation during their bortezomib treatment is recommended together with notification of possible adverse events not described or listed as uncommon in their severity.