S6020 Checkpoint Inhibitor Enteritis Masquerading as Refractory Celiac Disease

Introduction: Celiac disease (CD) is an autoimmune pathology triggered by gluten ingestion, resulting in small intestinal inflammation and malabsorption. Cardinal symptoms of CD are weight loss, nutrient deficiencies, and skin rashes with associated abdominal pain, bloating, and changes in bowel habits. In recent years, there has been a rise in immune checkpoint inhibitors (ICI) as cornerstone treatment for a variety of malignancies. A common immune-related adverse event (irAE) is development of immune-mediated colitis; however, in rare instances, development of de novo CD has been described. We present a case of ICI CD in a patient with pre-existing autoimmune CD. Case Description/Methods: A 53-year-old woman with a 7-year history of diet-controlled CD was diagnosed with stage III medullary colon cancer (MCC). When initially diagnosed with CD, her tissue transglutaminase (tTG) IgA was 190 U/ml (normal <15). After strict compliance with a gluten free diet (GFD), she achieved clinical and serologic remission. Following the detection of MCC she underwent a partial colectomy with adjuvant FOLFOX and ICI therapy. During treatment, the patient developed mild abdominal bloating and loose stools. Serologies revealed a tTG IgA of 4 U/ml and were again normal 1 month after cessation of ICI. She made small dietary changes including lactose avoidance with complete symptom resolution. She underwent an esophagogastroduodenoscopy (EGD) revealing mucosal inflammation and atrophic changes in the duodenum. Biopsies from the duodenum confirmed focally increased intraepithelial lymphocytes, focal villous atrophy, and crypt hyperplasia. Given normal celiac serologies, the absence of symptoms, and prior cessation of ICI therapy, glucocorticoids were not initiated. Discussion: This case elegantly illustrates an atypical presentation of ICI-related CD in a patient with a preexisting diagnosis of CD. To our knowledge, this is the only report of a patient with known CD predating the use of ICI with otherwise unexplained new endoscopic and histopathologic findings consistent with refractory CD. If this medication-induced condition is not recognized, the provider is tempted to treat with glucocorticoids and make unnecessary referrals to nutritional medicine, searching for inadvertent gluten ingestion. In asymptomatic patients, we would recommend an EGD to confirm resolution after completion of ICI and would consider serologic screening in patients with known autoimmune predispositions for CD prior to initiation of ICIs.