Pseudomembranous colitis following bortezomib therapy in a myeloma patient

The proteasome inhibitor, bortezomib, has antimyeloma activity even in myeloma cells refractory to multiple prior treatments. The most commonly reported adverse events in patients receiving bortezomib are sensory neuropathy, thrombocytopenia and gastrointestinal events. We report a patient with myeloma who developed pseudomembranous colitis after bortezomib treatment. Bortezomib has the boronic acid moiety which improves the specificity of proteasome inhibition and can be used as non-β-lactam-based β-lactamase inhibitors. This case indicates that gastrointestinal toxicities by bortezomib may be caused, in part, as a result of change in the colonization of colonic microflora.