Krishnan A, Lucas K, Maas L, Woreta TA. Differentiating fenbendazole-induced liver injury from immunotherapy hepatitis - the importance of structured causality assessment: A case report. World J Clin Cases 2026; 14(2): 116700 [DOI: 10.12998/wjcc.v14.i2.116700]
Corresponding Author of This Article
Tinsay A Woreta, MD, MPH, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, MD 21205, United States. tworeta1@jhmi.edu
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Gastroenterology & Hepatology
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Case Report
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This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Jan 16, 2026 (publication date) through Jan 23, 2026
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World Journal of Clinical Cases
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Krishnan A, Lucas K, Maas L, Woreta TA. Differentiating fenbendazole-induced liver injury from immunotherapy hepatitis - the importance of structured causality assessment: A case report. World J Clin Cases 2026; 14(2): 116700 [DOI: 10.12998/wjcc.v14.i2.116700]
World J Clin Cases. Jan 16, 2026; 14(2): 116700 Published online Jan 16, 2026. doi: 10.12998/wjcc.v14.i2.116700
Differentiating fenbendazole-induced liver injury from immunotherapy hepatitis - the importance of structured causality assessment: A case report
Arunkumar Krishnan, Kaleb Lucas, Laura Maas, Tinsay A Woreta
Arunkumar Krishnan, Department of Supportive Oncology, Atrium Health Levine Cancer, Atrium Health Wake Forest Baptist Comprehensive Cancer Center, Charlotte, NC 28204, United States
Arunkumar Krishnan, Department of Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27101, United States
Kaleb Lucas, Department of Medicine, Sinai Hospital of Baltimore, Baltimore, MD 21215, United States
Laura Maas, Tinsay A Woreta, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States
Co-first authors: Arunkumar Krishnan and Kaleb Lucas.
Author contributions: Krishnan A and Lucas K conceptualized and designed the research, performed interpretation of data and wrote the original draft, and they contributed equally to this manuscript and are co-first authors; Krishnan A, Maas L, and Woreta TA performed the review and editing of the draft; Woreta TA supervised the project. All authors revised the manuscript for important intellectual content and approved the final version of the article, including the authorship list.
Informed consent statement: Informed written consent was obtained from the patient for publication of this report and any accompanying images.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Tinsay A Woreta, MD, MPH, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, MD 21205, United States. tworeta1@jhmi.edu
Received: November 18, 2025 Revised: December 13, 2025 Accepted: January 5, 2026 Published online: January 16, 2026 Processing time: 59 Days and 13.2 Hours
Abstract
BACKGROUND
Drug-induced liver injury poses a diagnostic challenge in oncology patients, especially those on immune checkpoint inhibitors, because symptoms often overlap with immune-mediated hepatitis. The increasing use of social media has led people to self-administer veterinary anthelmintics like fenbendazole for cancer, often at high doses and without medical guidance, despite limited data on safety or effectiveness.
CASE SUMMARY
We report a case of a 47-year-old woman with metastatic colon cancer on nivolumab/relatlimab who developed severe hepatocellular liver injury after increasing her self-administered dose of fenbendazole. A detailed medical and temporal history, supported by a Roussel Uclaf Causality Assessment Method score of 8 (probable), identified fenbendazole as the most likely cause. Rapid biochemical improvement occurred after stopping the drug, with safe reintroduction of immunotherapy and no recurrence of liver injury.
CONCLUSION
This case emphasizes the importance of thorough medication history-taking and structured causality assessment to distinguish between unregulated drug-induced liver injury and immune-related adverse events in cancer care. The use of social media to promote alternative therapies necessitates proactive patient counseling due to significant liver risks, and careful diagnostic evaluation can prevent unnecessary immunosuppression or treatment delays.
Core Tip: A middle-aged woman with metastatic colon cancer on immune checkpoint immunotherapy presented with acute hepatocellular injury. This case highlights severe fenbendazole-induced hepatocellular injury in an oncology patient receiving immune checkpoint inhibitors, where timing and causality assessment were vital for accurately attributing the liver injury. Social media-driven self-medication is becoming increasingly common among cancer patients, with fenbendazole doses often far exceeding veterinary recommendations. Prompt recognition and removal of the offending agent can allow safe continuation of immunotherapy and prevent unnecessary immunosuppression. A thorough approach to medication history-taking, including non-prescription and alternative drugs, is essential when evaluating unexplained acute liver injury.
