A 36-year-old man was hospitalized for suspected relapsing lymphoma. Three days after endoscopic gastric biopsy, he developed acute dyspnea, tachypnea (44/min), tachycardia (144/min), and low-grade fever while in the ward. He had agitation, jaundice, and generalized livedo reticularis (Fig. 1). On ICU admission, his blood was noticed to precipitate quickly, even in the EDTA phlebotomy tube (Fig. 2a). The hemoglobin level was undetectable in the laboratory and blood gas analyzer. Laboratory results included high lactate dehydrogenase (1632 IU/L), low haptoglobin (0.17 g/L), positive Coombs test (anti-C3d antibodies 2+), and positive cold agglutinin titer. Blood smear showed red blood cell (RBC) clumping (Fig. 2b, c). He was diagnosed with cold agglutinin disease. The patient required intubation and vasopressors. He received 11 units of packed RBCs via warmers and was treated with rituximab. He progressed rapidly to multiorgan failure and death on the third ICU day. The gastric biopsy showed peripheral T cell lymphoma.