Chapter 34, Ep 1 of 4: Solid Organ Transplant GI Disease

Episode one of the GI in the Immunocompromised Host chapter starts with a single recognition move: a transplant recipient on calcineurin inhibitor plus mycophenolate plus prednisone with diarrhea could be any of five entities at once, and time since transplant is the variable that reorders the differential. The first month belongs to the surgeon, the one-to-twelve-month window belongs to opportunistic infection, and beyond a year belongs to cumulative toxicity and malignancy. From there the reasoning runs on enzymes: donor-recipient serostatus and UL97 versus UL54 for CMV resistance, CYP3A4 for the calcineurin inhibitor trap, and dose-dependent crypt exposure for mycophenolate enteropathy. Sitting over all of it, Epstein-Barr virus drives the post-transplant lymphoproliferative disorder that responds first to reducing the immunosuppression that allowed it.   Topics covered The five-entity transplant diarrhea differential Time since transplant as the organizing variable CMV serostatus stratification and valganciclovir prophylaxis CMV colitis diagnosis and base-of-ulcer biopsy Ganciclovir resistance and the UL97 versus UL54 pathway Mycophenolate enteropathy and its histologic mimics Calcineurin inhibitor toxicity and CYP3A4 drug interactions Post-transplant lymphoproliferative disorder and EBV   Key decisions Before any test or scope, place the patient on the transplant timeline: first month surgical, one to twelve months opportunistic, beyond a year cumulative toxicity and malignancy. Use valganciclovir nine hundred milligrams daily for solid organ transplant CMV prophylaxis, not letermovir, and give the D-plus R-minus mismatch the longest course at every organ. Diagnose CMV colitis with a biopsy from the ulcer base plus immunohistochemistry, because inclusions concentrate in granulation tissue and H and E misses up to half of cases. Treat ganciclovir-resistant CMV from a UL97 mutation with foscarnet or maribavir, and recognize that UL54 mutations produce resistance to both ganciclovir and foscarnet. Manage mycophenolate enteropathy by mechanism: reduce the dose twenty-five to fifty percent or convert to enteric-coated mycophenolic acid, reserving azathioprine for refractory cases. Screen every new prescription in a transplant patient against the CYP3A4 list, because azoles, erythromycin and clarithromycin, and verapamil or diltiazem push calcineurin inhibitor levels toxic. Treat CD20-positive PTLD by reducing immunosuppression first, then adding rituximab, escalating to R-CHOP only in patients without complete response after induction.   For the full chapter with MCQs, tables, and primary-guideline references, visit www.boardpearls.com. Questions or feedback: [email protected]. (00:00) - The five-entity differential and the organizing idea (01:00) - Time since transplant reorders everything (02:07) - CMV serostatus and valganciclovir prophylaxis (07:08) - Mycophenolate enteropathy and its mimics (08:57) - Calcineurin inhibitor toxicity and CYP3A4 (11:45) - Post-transplant lymphoproliferative disorder and EBV (15:37) - Pulling the solid organ transplant half together