]> 2026-07-31T14:30:21+00:00 WBR0955 0 en Direct effect of heparin on platelet activation ''' Correct ''' : This patient has type I heparin-induced thrombocytopenia that is typically characterized by a slight fall in platelet count (< 50%) within the first two days after heparin initiation and often returns to normal with continued heparin administration. The mechanism of the thrombocytopenia is nonimmune and appears to be due to a direct effect of heparin on platelet activation. Warfarin induced thrombocytopenia Antibodies against the heparin-platelet factor 4 complex ''' Incorrect ''' : Immune-mediated HIT is associated with a fall in the platelet count of >50 percent that typically occurs 5 to 10 days after the initiation of heparin therapy which is not seen in this patient. Antibodies against GP Ib/V/IX surface glycoprotein ''' Incorrect ''' : Membrane GPIb/IX of phagocytosed platelets are processed, and their digested peptides are presented by macrophages to autoreactive HLA-restricted CD4+ T cells in immune thrombocytopenic purpura. It is not related to initiation of heparin. Antibodies against GP IIb/IIIa surface glycoprotein Emergency Room A 50 year old woman comes to the emergency department with complaints of shortness of breath and chest pain. She has these symptoms for the past one day. On further review of history she reveals a recent history of travel outside the United States 3 days back. Her past history is otherwise insignificant and her family history is unremarkable. She has smoked one pack of cigarette for the past 10 years. She attained menopause at the age of 48 and not on any medications. Her vitals are temperature: 36.7 C, blood pressure: 140/80 mmHg, pulse: 80/min and respiration: 15/min. The patients pulse oximetry shows 95 % on 4-litres of oxygen. All system examinations are normal. V/Q scan shows high probablity for pulmonary embolism. Her laboratory values comes as : Hb : 13 g/dl Hct : 38% RBC’s : 2.5 million/cmm WBC’s : 6000/cmm Platelet’s : 300,000/cmm PT : 13 sec (N 11-15 sec) INR : 1.03 You start the patient on unfractionated heparin and warfarin. Her symptoms resolve the next day and a repeat CBC on the second day reveals a platelet count of 160,000/cumm. What is the most likely cause of her thrombocytopenia? A Hematology 2020-10-28T02:10:56Z 2459150.5909259 WBR0955