Mycophenolate mofetil (MMF) is an immunosuppressive agent, the gastrointestinal side effects of which include abdominal pain, diarrhoea, and vomiting. MMF may also cause symptomatic colitis, although it is a rare condition. We present herein the case of a boy with chronic kidney disease, lasting since the neonatal period, and caused by WT1 gene mutation. The patient developed colitis during an immunosuppressive therapy applied after a kidney transplant. Histopathology of intestinal biopsy specimens revealed features of MMF-related colitis. A modification of the immunosuppressive treatment and the implementation of a nutritional programme to the patient resulted in the disappearance of clinical signs and helped in a gradual body weight gain.