Waldenström macroglobulinaemia presenting with suspected protein-losing enteropathy and nodular polypoidal duodenal mucosal changes: a case report

Gastrointestinal involvement in Waldenström macroglobulinaemia is uncommon, and presentation with features suggestive of protein-losing enteropathy and nodular polypoidal duodenal mucosa is particularly rare. A 67-year-old man presented with persistent, non-bloody diarrhoea, progressive anorexia, and significant weight loss for three years. Laboratory evaluation revealed profound hypoalbuminaemia and mild normocytic anaemia, with preserved hepatic and renal function. Extensive gastrointestinal investigations, including upper and lower endoscopies with biopsies, revealed nodular polypoidal duodenal abnormalities. Histopathological examination repeatedly showed intravascular fibrinoid material, which can occur in various vascular or inflammatory conditions, but did not establish a definitive diagnosis. Despite symptomatic management, his condition gradually worsened. Bone marrow aspiration and biopsy showed lymphoplasmacytic infiltration with an immunophenotype supporting lymphoplasmacytic lymphoma. Subsequent serum protein electrophoresis demonstrated a monoclonal protein, and the overall clinicopathological findings supported a diagnosis of lymphoplasmacytic lymphoma/Waldenström macroglobulinaemia. Treatment with dexamethasone, rituximab, and cyclophosphamide led to marked clinical and biochemical improvement, with resolution of diarrhoea and normalisation of serum albumin, suggesting an association between Waldenström macroglobulinaemia and the gastrointestinal manifestations. This case highlights an unusual gastrointestinal manifestation of Waldenström macroglobulinaemia presenting with chronic diarrhoea and severe hypoalbuminaemia suggestive of protein-losing enteropathy. When conventional gastrointestinal investigations are unrevealing, underlying haematological malignancies should be considered in the differential diagnosis of unexplained hypoalbuminaemia and chronic diarrhoea.