Abstract: TH-PO0850
Not All Diarrhea on Mycophenolate Is Mycophenolate: Losartan-Associated Enteropathy Mimicking Immunosuppression Toxicity
Session Information
- Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
- 1900 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
Authors
- Diaz del Castillo Guzman, Humberto, Cleveland Clinic, Cleveland, Ohio, United States
- Lee, Ruth Diana, Cleveland Clinic, Cleveland, Ohio, United States
- Almaani, Salem, Cleveland Clinic, Cleveland, Ohio, United States
- Calle, Juan C., Cleveland Clinic, Cleveland, Ohio, United States
Introduction
Diarrhea is common in patients receiving immunosuppressive therapy, with mycophenolate mofetil (MMF) as a common cause. Angiotensin receptor blockers (ARBs) are also widely prescribed in kidney disease. ARB-associated enteropathy has been increasingly recognized since olmesartan was linked to sprue-like enteropathy in 2012, but losartan-associated enteropathy remains exceedingly rare. A literature review identified no prior histopathologically confirmed cases of losartan-associated enteropathy.
Case Description
A 23-year-old woman with relapsing nephrotic syndrome due to FSGS was admitted for intractable diarrhea. Her disease course included intermittent high-dose corticosteroids, long-term MMF since early childhood, and prior calcineurin inhibitor exposure.
MMF was started 6 weeks prior to presentation in the setting of a disease relapse, raising immediate concern for MMF-induced gastrointestinal toxicity despite prior tolerance. On admission, medications included MMF, tacrolimus, prednisone, and had been on losartan for at least 15 months prior to presentation. Celiac serologies were negative. MMF was held early because of persistent symptoms. Cross-sectional imaging demonstrated findings concerning for colitis, prompting EGD and colonoscopy.
Duodenal biopsies demonstrated intraepithelial lymphocytosis with preserved villous architecture and without significant crypt apoptosis, findings characteristic of ARB-associated enteropathy and not typical of MMF-associated injury. Colonic biopsies showed only mild nonspecific crypt apoptosis. Given chronic losartan exposure and absence of convincing MMF-related pathology, losartan was identified as the most likely cause of symptoms. Diarrhea improved significantly after losartan discontinuation while continuing MMF.
Discussion
Although extremely rare, losartan may cause ARB-associated enteropathy and may represent an underrecognized cause of chronic diarrhea. In a review of 4,337 FDA adverse event reports of ARB-associated sprue-like enteropathy, 98% involved olmesartan, highlighting the rarity of non-olmesartan cases. In patients receiving multiple medications with overlapping gastrointestinal toxicity profiles, histopathologic evaluation is critical in distinguishing ARB-associated enteropathy from MMF-related injury and may prevent unnecessary discontinuation of essential immunosuppressive therapy.