(1707) Post-Lung Transplant Chronic Diarrhea: A Rare Case of Mycophenolate-Induced Colitis

Introduction: Mycophenolate Mofetil (MMF) is an antimetabolite commonly used to prevent rejection of solid organ transplants. This report presents a rare case of MMF-induced colitis (MIC) in a lung transplant recipient with a concurrent Sapovirus gastrointestinal infection, which led to a delayed diagnosis.

Description: A 71-year-old female underwent bilateral lung transplant for idiopathic pulmonary fibrosis and received basiliximab, methylprednisolone, and mycophenolate for induction, followed by maintenance therapy with tacrolimus, mycophenolate, and prednisone. Prophylactic medications included sulfamethoxazole-trimethoprim and valganciclovir. The immediate post-transplant course was uneventful, except that the patient developed Clostridium difficile diarrhea, which responded well to oral vancomycin therapy. Two months post-transplant, she was admitted for diarrhea, renal failure, and generalized weakness. Although she had 2 to 3 loose stools daily, she denied fever, vomiting, hematochezia, or abdominal pain. Laboratory findings were unremarkable except for an elevated serum creatinine level of 2.1 mg/dl (baseline: 0.9 mg/dl), and stool PCR confirmed Sapovirus infection. Following supportive care, the patient was discharged with improved kidney function. However, her diarrhea worsened over the subsequent 2 weeks, accompanied by vomiting, reduced appetite, deteriorating kidney function, and new-onset anemia. On repeat infectious workup, Sapovirus was detected again in the stool. Endoscopy was performed which revealed an unremarkable duodenal biopsy but colon biopsy demonstrated features consistent with mycophenolate-induced colitis (MIC), including cryptic distortion, apoptosis with apoptotic debris, and an edematous lamina propria infiltrated with eosinophils. Immunostains for CMV, Adenovirus, Herpes Simplex I, and II were negative. Switching from MMF to azathioprine resulted in complete symptom resolution within 2 weeks.

Discussion: The diagnosis of MMF-induced colitis necessitates comprehensive infectious workup and histopathologic examination to differentiate it from conditions such as Post-Transplant Lymphoproliferative Disorder, Graft Vs. Host Disease (GVHD), and Inflammatory Bowel Disease. Management involves supportive care and discontinuation of the causative immunosuppressive agent.