A Wolf in Sheepʼs Clothing: A Unique Case of Zollinger-Ellison Syndrome Masquerading as Ileal Crohnʼs Disease

Abstract

Zollinger-Ellison Syndrome (ZES) often presents with peptic ulcer disease, symptoms of gastroesophageal reflux disease (GERD) and chronic diarrhea. This is the result of gastric acid hypersecretion secondary to ectopic gastrin production, typically, from a pancreatic or duodenal neuroendocrine tumour (NET). This report presents a unique case of a patient initially thought to have small bowel Crohn's disease (CD). Incidental discovery of a gastrinoma led to a diagnosis of ZES. A 57 year old male was referred to an outside gastroenterology clinic for evaluation and management of a longstanding history of dyspeptic symptoms and diarrhea. On review of his history, he had a repair of a perforated jejunal ulcer 3 years prior, presumed to have been related to intermittent use of non-steroidal anti-inflammatory drugs. He remained on chronic proton-pump inhibitor therapy, with adequate control of his dyspepsia. As part of his work-up for chronic diarrhea, he underwent upper endoscopy and colonoscopy. The upper tract was grossly normal, and biopsies showed mild chronic gastritis. Colonoscopy showed a grossly and histologically normal colon, but the terminal ileum could not be intubated. Subsequent CT enterography showed 2 fibrotic strictures of the distal ileum, leading to a diagnosis of Crohn's disease, and prompting referral to our Inflammatory Bowel Diseases Clinic. Incidental note was made of a 5cm mass at the tail of the pancreas, consistent with a probable NET, prompting immediate surgical referral. By the time of his presentation to our clinic, he was 2 months post the resection of his tumour, which was proven histologically to be a gastrin-producing NET. He reported complete resolution of his chronic diarrhea and dyspepsia. A diagnosis of ZES was entertained and a work-up for MEN-1 was initiated. Brain MRI demonstrated a 2 mm pituitary microadenoma, consistent with possible MEN-1. In the literature, 75% of gastrointestinal ulceration in ZES occur in the first portion of the duodenum with ulcers less likely in the distal duodenum and jejunum. There are no reports of ZES associated ulceration occurring in the ileum. This patient's ileal strictures are hypothesized to be secondary to ulcers due to the gastrinoma. This would offer a unifying diagnosis for this patient's findings and would explain the resolution of his symptoms with resection of his tumour.