Multiple Endocrine Neoplasia Type 1 Presenting as Recurrent Overt Gastrointestinal Bleeding and Ulceration: A Diagnostic Challenge.

Multiple endocrine neoplasia type 1 (MEN1) is a multisystem endocrine disorder marked by tumors of the parathyroids, pancreatic islet cells, and pituitary gland. Although most cases are inherited through an autosomal dominant pattern, a proportion arises through sporadic mutation. As the clinical presentation is highly variable, it often leads to diagnostic delay in patients with de novo mutations. We report a 48-year-old man with no family history and a past medical history of renal calculi with intermittent hematuria. Over several months, he had multiple hospitalizations due to progressive epigastric pain and melena. Initial imaging suggested a localized small bowel perforation, which was treated conservatively. Endoscopic evaluation revealed severe esophagitis and duodenitis with biopsies suggesting peptic duodenitis. His symptoms were initially attributed to peptic ulcer disease and later to possible inflammatory bowel disease (IBD), and he was managed with proton pump inhibitors (PPIs) and steroids. Despite this, he continued to represent similarly and also developed an episode of upper-limb thrombophlebitis requiring anticoagulation. Biochemical investigations demonstrated persistent hypercalcemia, elevated parathyroid hormone, and significantly raised fasting gastrin levels whilst off high-dose PPI, raising suspicion for MEN1 syndrome. Functional imaging identified a parathyroid adenoma and multiple pancreatic and duodenal neuroendocrine tumors. Genetic testing confirmed a pathogenic MEN1 mutation. He was referred for parathyroidectomy followed by total pancreatectomy with duodenectomy, while first-degree relatives were offered genetic screening. This case highlights the diagnostic complexity of MEN1 in the absence of a family history, in which gastrointestinal ulcerations with bleeding, fleeting thrombophlebitis, and hypercalcemia may serve as early clinical clues.