Apoptotic colonopathy under immunosuppression: mycophenolate-related effects and beyond

Diarrhea developing in patients under immunosuppression has a variety of underlying causes. A broad spectrum of histological findings can be found in intestinal biopsies taken for the diagnostic workup of diarrhea including a pathologically increased proportion of epithelial cell apoptosis in the colon, for which the descriptive term 'apoptotic colonopathy' was coined. In recent years, the immunosuppressive drug mycophenolate (mycophenolic acid, MPA) has been identified as a prototypical cause of apoptotic colonopathy, but other conditions may show similar or overlapping histological pictures.

Cases of likely or possible MPA colonopathy (n = 18) were retrospectively identified from the archive files. Clinical information on patient history, clinical presentation and endoscopic findings were recorded. All cases were routinely processed, i.e. stained by hematoxylin and eosin (HE) stain, optionally supplemented by special histochemical and immune stains.

Histopathological hallmarks of MPA treatment-related changes in the colon mucosa are reviewed with respect to the major histopathological differential diagnoses including normal and near-normal findings, infectious diseases, graft-versus-host disease and inflammatory bowel diseases. Furthermore, the challenge of multiple concomitant pathologies while on MPA treatment, in particular infectious diseases, is discussed, and some open questions concerning the effects of MPA on colon pathology are pointed out.