Unusual cause of duodenal cobblestoning

Monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) is a rare and highly aggressive primary intestinal lymphoma, accounting for <5% of T-cell lymphomas and typically affecting the jejunum and ileum. It often presents with non-specific gastrointestinal symptoms, making diagnosis challenging. A patient in their 70s presented with progressive generalised oedema, unintentional weight loss, hypoalbuminaemia and anaemia. A recent positive faecal immunochemical test prompted an outpatient colonoscopy before admission, which was unremarkable. CT of the thorax, abdomen and pelvis demonstrated extensive subcutaneous oedema, ascites, small bilateral pleural effusions and diffuse small bowel thickening. Urinalysis showed no proteinuria, reducing the likelihood of a renal cause of oedema. Upper gastrointestinal endoscopy revealed an oedematous gastric body and a cobblestone appearance of the duodenum. Duodenal biopsies showed diffuse intraepithelial lymphocytosis with epitheliotropism by monotonous small to intermediate lymphoid cells. The lymphoid cells were positive for CD3, CD8 and CD56, with loss of CD5 expression and negative for CD20, CD10, CD4 and CD30. The Ki-67 proliferation index was approximately 50%. Next-generation sequencing confirmed T-cell receptor clonality and identified pathogenic variants in KRAS and STAT5B, supporting the diagnosis of MEITL. The patient was treated with anthracycline-based chemotherapy (CHOP regimen). Unfortunately, after completing four cycles, they developed bowel obstruction three months after diagnosis and subsequently died. This case highlights the importance of recognising abnormal duodenal mucosal patterns, such as cobblestoning, during endoscopy and obtaining biopsies even in the absence of classical coeliac disease features, as this may facilitate earlier diagnosis of rare but aggressive entities such as MEITL.