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Immune checkpoint inhibitor associated diarrhoea
  1. Amin Al-Hussainy1,
  2. Joss Adams2,
  3. Jon Simmons2 and
  4. James Kennedy2
  1. 1Wexham Park Hospital, Slough, UK
  2. 2Royal Berkshire Hospital, Reading, UK
  1. Correspondence to Dr Amin Al-Hussainy; 97aamin{at}


A man in his 80s was undergoing immunotherapy with pembrolizumab, an anti-PD-1 monoclonal antibody, following his diagnosis of adenocarcinoma of primary lung origin. 24 weeks into treatment, the patient reported experiencing loose stools associated with malaise and poor appetite but no further symptoms. This progressed in frequency and a clinical diagnosis of grade 2 immune checkpoint inhibitor colitis was made. Management with oral prednisolone was commenced but symptoms persisted. Common enteric infections had been ruled out, as were coeliac disease and hyperthyroidism. Flexible sigmoidoscopy and colonoscopy results were not in keeping with colitis, having revealed normal looking mucosa. Following this, a faecal elastase level was found to be low. A diagnosis of pembrolizumab-induced pancreatic exocrine insufficiency was made, and stool frequency and consistency swiftly improved following the use of pancreatic enzyme replacement therapy.

  • Gastroenterology
  • Lung cancer (oncology)
  • Unwanted effects / adverse reactions

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  • Contributors AA-H was responsible for drafting the majority of the text and its critical revision. JS and JK reviewed the patient in the outpatient gastroenterology clinic. JA is directly involved in the patient’s oncological care. JA, JS and JK critically revised the article, making significant contributions to its content and gave final approval for its publication. All authors gave final approval of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.