A 44-year-old female developed a catastrophic thrombotic syndrome following allogeneic stem cell transplantation for acute lymphoblastic leukemia. In the context of chronic graft versus host disease, she developed a lethal multi-system thrombotic state as evidenced by stroke, renal failure and cardiac thrombi in association with elevated anticardiolipin antibody. The case is discussed in the framework of the existing literature and derives clinical practice recommendations for this rare but clinically devastating entity.