Clinical Challenges and Images in GI: Image 2, Intestinal Waldenström macroglobulinemia

Image 2 Question: A 76-year-old woman was admitted to the hospital because of an 8-month history of diarrhea (up to 10 bowel movements a day), progressive weight loss (12 kg), and fatigue. Four years before admission she had had a Billroth II resection for gastric cancer, and 1 year before, she’d had a transient ischemic attack without sequelae. On physical examination, she presented severe wasting and a mild leg edema. Blood tests showed hemoglobin, 10.5 g/dL; white cell count, 3500/mm3; abnormal coagulation (prothrombin time, 34.6 seconds; partial thromboplastin time, 56 seconds); low total and fractional cholesterol; total protein, 4.7 g/dL; albumin, 2.2 g/dL; low immunoglobulin (Ig)G; normal IgA; high IgM (860 mg/dL); normal serum electrophoresis; very high rheumatoid factor (6,260 U/mL) and C-reactive protein (32.1 mg/dL). All autoantibodies were negative except anticardiolipin IgM. Urinalysis was normal. The stool culture and the parasitologic examination were negative, but there was steatorrhea and a positive fecal occult blood testing.A colonoscopy was performed, showing a normal mucosa throughout the colon but a pale, granular mucosa in the ileum (Image A). Contrast-enhanced computed tomography (CT) of the abdomen showed a thickening of the intestinal wall and a mild splenomegaly (Image B). Although esophagogastroduodenoscopy had been performed 1 year before admission, we decided to repeat the examination, integrating it with a videocapsule endoscopy. No relapse of the cancer was present, but the entire small bowel showed a whitish and granular mucosa with some erosions (Image C). Specimens for histologic examination and immunofluorescence were taken. What is the diagnosis?