An Extremely Rare Cause of Protein-Losing Enteropathy: Waldenström Macroglobulinemia.

Protein-losing enteropathy (PLE) results in the abnormal loss of proteins through the gastrointestinal tract, leading to malabsorption and hypoalbuminemia. A rare etiology of PLE is Waldenström macroglobulinemia (WM), a hematological malignancy characterized by immunoglobulin M (IgM) monoclonal gammopathy. We present a case of a 66-year-old man with a history of small bowel bacterial overgrowth and lactose intolerance, admitted for worsening gastrointestinal symptoms, including abdominal discomfort, bloating, and watery diarrhea. He had experienced significant weight loss and anasarca over 6 months. Laboratory tests indicated hypoproteinemia, hypoalbuminemia, and elevated IgM levels, accompanied by abnormal stool studies. Imaging showed no significant findings, while endoscopic evaluation revealed lymphangiectasia-like changes in the small bowel. Biopsy results demonstrated proteinaceous material in dilated villi and IgM deposition. The diagnosis of WM was confirmed by bone marrow biopsy. Thus, WM should be considered when evaluating unexplained PLE, particularly with associated gastrointestinal symptoms and elevated IgM levels.