Snapshot A 60-year-old woman presents after a 12-hour train ride with right-sided crampy leg pain. She is currently on hormone-replacement therapy for menopausal symptoms. On exam, the circumference on the right calf is larger than the left. An ultrasound shows a lower extremity DVT. She is started on heparin. Two days later, her platelets come back at 24,000/mm3. They were previously 30,000/mm3. Her labs are monitored routinely, and her platelets returned to baseline after a few days. Introduction Decreased platelets due to exposure to heparin Epidemiology Female > male (1.7x) Risk factors login to view 2 more bullets etiology Type I HIT login to view 4 more bullets Type II HIT login to view 10 more bullets Presentation Type I - asymptomatic Type II - symptoms login to view 12 more bullets studies Complete blood count login to view 2 more bullets ↑ bleeding time Normal PT/PTT Presence of anti-PF4-heparin login to view 2 more bullets Differential Diagnosis DIC ITP TTP HUS Treatment Prevention login to view 1 more bullet First step login to view 1 more bullet Subsequent steps login to view 3 more bullets PLT infusion is contraindicated login to view 1 more bullet Complications Thrombosis Prognosis Mortality 5-10% in patients with HIT type II login to view 1 more bullet