Abstract
A 64-year-old man was found to have a nodule in his right lung. He also complained of nausea and abdominal pain during the clinical course. Esophagogastroduodenoscopy revealed a duodenal ulcer associated with severe stenosis and a suspicion of malignancy. However, three subsequent biopsies revealed no evidence of malignancy. The fourth biopsy showed scattered large eosinophilic cells with an eccentric nucleus, leading to a diagnosis of Russell body duodenitis (RBD). RBD is an extremely rare disease, and little is known about its etiology and clinical course. The pathogenesis of RBD is discussed based on our experience with this case.