Background: Myelodysplastic syndrome (MDS) commonly causes chronic anemia through ineffective hematopoiesis, while gastrointestinal bleeding from small-bowel neuroendocrine tumors (NETs) is uncommon and may evade conventional endoscopic evaluation.
Case Presentation: An 85-year-old man with MDS, small-bowel carcinoid tumor, atrial fibrillation on apixaban, and systolic heart failure presented with dizziness, dyspnea, and weakness. Hemoglobin was 4.1 g/dL, accompanied by hypotension, atrial fibrillation with rapid ventricular response, melena, and positive fecal occult blood testing. Troponin increased from 2,865 to >50,000 ng/L without chest pain, consistent with severe supply-demand myocardial injury from profound anemia, hypotension, and tachyarrhythmia. Apixaban was withheld, and packed red blood cell transfusions increased hemoglobin to 9.1 g/dL. Esophagogastroduodenoscopy revealed no bleeding source. Given persistent suspicion for small-bowel hemorrhage and the known carcinoid tumor, mesenteric angiography was performed with selective transcatheter arterial embolization. Hemoglobin remained stable without recurrent overt bleeding.
Conclusion: Worsening anemia in patients with MDS should not automatically be attributed to ineffective hematopoiesis. Concurrent gastrointestinal blood loss, including bleeding associated with small-bowel NETs, should be investigated when clinical findings suggest an additional source.