A 70-year-old male presented in the emergency clinic with a few-day history of pain and swelling in his left foot. His past history was significant for repeated red blood cell (RBC) transfusions for anemia. Comorbidities included hypertension, diabetes mellitus, and chronic kidney disease. Examination showed pallor and a gangrenous foot with absent peripheral pulses. Complete blood count showed hemoglobin (Hb) 6.2 g/dL, hematocrit (Hct) 2.4%, RBC count 0.22 3 1012/L, mean corpuscular volume (MCV) 109.1 fL, mean corpuscular Hb (MCH) 281.8 pg, MCH concentration 258.3 g/dL, white blood cell (WBC) count 8.0 3 109/L, and platelet (PLT) count 433 3 109/L. Blood chemistry showed total bilirubin of 1.2 mg/dL, direct bilirubin 0.6 mg/dL, alanine aminotransferase 20 IU/L, and creatinine 1.8 mg/dL. Urine showed microscopic hemo-globinuria. Viral hepatitis workup was negative. Computed tomography (CT) angiogram showed no deep venous thrombo-sis or arterial stenosis. Provisional diagnosis was acral gangrene complicating diabetes. Two units of RBCs were arranged perioperatively for amputation of his left leg. Blood sample for group and crossmatch showed cold agglutination that.