Rapid Development of Pernicious Anemia Unmasking Underlying Gastric Adenocarcinoma

Gastric cancer is one of the most common malignancies, often detected at later stages as patients remain asymptomatic until later stages. Pernicious anemia (PA), a well-known cause of vitamin B12 deficiency, is a classic risk factor for gastric cancer. Patients with PA usually present with megaloblastic anemia and peripheral neuropathy; however, they can also present with nonspecific symptoms. We describe below the case of a 56-year-old male who presented with symptoms of nausea, vomiting, and fatigue. Initial lab work revealed severe B12 deficiency, pancytopenia, and intramedullary hemolysis warranting endoscopy that revealed a gastric fundus mass significant for adenocarcinoma on biopsy.