A unique case of protein-losing enteropathy in the setting of immune checkpoint inhibition case report

Protein-losing enteropathy (PLE) is a well described entity, typically associated with autoimmune disorders such as Systemic Lupus Erythematosus (SLE). However, there is only one prior case reported on the association between PLE and the use of immune checkpoint inhibitors. We describe a case of PLE presenting in a patient in their 70’s with muscle-invasive urothelial bladder cancer that developed while on treatment with pembrolizumab, radiation and gemcitabine for her cancer. The patient presented initially with progressive edema and hypoalbuminemia, and diffuse small bowel thickening on CT imaging without associated upper or lower gastrointestinal symptoms. Endoscopy with biopsy was performed demonstrating normal gastric and small bowel epithelium. A stool test for alpha-1-antitrypsin demonstrated increased clearance consistent with fecal protein loss and a diagnosis of PLE, presumed immune-related. She was promptly initiated on systemic corticosteroids with brisk resolution in her symptoms and normalization of serum albumin levels. This case highlights a rare immune-related adverse event, PLE, that should be considered in patients who develop hypoalbuminemia and its clinical sequelae after immune checkpoint inhibition therapy without evidence of colitis.