Abstract
RATIONALE: Antiphospholipid antibody syndrome and protein S/C deficiency are diseases that are sometimes complicated by thrombus, and heparin-induced thrombosis (HIT) has also been reported. PATIENT CONCERNS: A male patient in his 60s with elevated D-dimer and superior mesenteric thrombus and portal vein thrombus underwent partial small intestine resection and thrombectomy. After administration of heparin, aortic thrombosis and pulmonary embolism occurred along with rapid thrombocytopenia. DIAGNOSIS: The patient was diagnosed with HIT combined with protein S deficiency and antiphospholipid antibody syndrome. INTERVENTIONS AND OUTCOMES: Heparin administration was discontinued, and plasma exchange with fresh frozen plasma replacement and argatroban administration were started. These treatments reduced D-dimer, restored platelet counts, and improved thrombosis. LESSONS: Although HIT alone can cause severe arteriovenous thrombosis, our case suggests that it is important to search for the underlying procoagulant factors.