WBR0956

Author	[[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Emergency Room
Sub Category	SubCategory::Hematology
Prompt	[[Prompt::A 62 year old woman comes to the emergency department with complaints of shortness of breath and chest pain. She was in her usual state this morning but suddenly developed these symptoms. Her past history is otherwise insignificant and her family history is unremarkable. She is a chronic smoker and smoked two packs of cigarette for the past 25 years. She occasionally consumes alcohol. She attained menopause at the age of 50 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 92 % on 4-litres of oxygen. All system examinations are normal. V/Q scan of the chest shows high probablity for pulmonary embolism. Her intial laboratory values are : Hb : 11 g/dl Hct : 37% RBC’s : 3 million/cmm WBC’s : 8000/cmm Platelet’s : 300,000/cmm PT : 13 sec (N 11-15 sec) APTT : 30 sec (N 25-40 sec) BT : 7 min (N 2-7 min) INR : 1.06 You start the patient on unfractionated heparin and warfarin. Her symptoms gradually resolve over the next five days. On the 7th day, she complaints of pain and pallor in the right arm. Examination of the right extremity reveals pale, tender arm with diminished peripheral pulses. A repeat CBC reveals Hb : 12 g/dl Hct : 37.5% RBC’s : 2.8 million/cmm WBC’s : 10000/cmm Platelet’s : 60,000/cmm PT : 19 sec (N 11-15 sec) APTT : 60 sec (N 25-40 sec) BT : 11 min (N 2-7 min) INR : 2 What is the most likely cause of her symptoms ?]]
Answer A	AnswerA::Heparin induced skin necrosis
Answer A Explanation	[[AnswerAExp:: Incorrect  : Skin necrosis at the site of heparin injections is a well-described complication of treatment with unfractionated or LMW heparin, and should immediately suggest the presence of HIT. Affected patients have heparin-dependent antibodies but may not develop thrombocytopenia.]]
Answer B	AnswerB::Heparin induced thrombocytopenia
Answer B Explanation	[[AnswerBExp:: Incorrect  : The appearance of otherwise unexplained thrombocytopenia, thrombosis associated with thrombocytopenia, a platelet count which has fallen 50 percent or more from a prior value, or necrotic skin lesions at heparin injection sites should raise the possibility of heparin-induced thrombocytopenia (HIT) in any patient begun on heparin therapy within the preceding 5 to 10 days.]]
Answer C	AnswerC::Warfarin induced skin necrosis
Answer C Explanation	[[AnswerCExp:: Incorrect  : Warfarin induced skin necrosis appears to be mediated by the rapid reduction of protein C levels on the first day of therapy, which induces a transient hypercoagulable state. The skin lesions may occur on the extremities, breasts, trunk, and penis and marginate over a period of hours from an initial central erythematous macule. Warfarin induced skin necrosis is not associated with thrombocytopenia.]]
Answer D	AnswerD::Disseminated intravascular coagulation
Answer D Explanation	[[AnswerDExp:: Incorrect  : The diagnosis of DIC is suggested by the history (eg, sepsis, trauma, malignancy), clinical presentation of bleeding and thrombosis, moderate to severe thrombocytopenia (<100,000/microL) and the presence of microangiopathic changes on the peripheral blood smear. The diagnosis is confirmed by the evidence of both increased thrombin generation (eg, decreased fibrinogen, prolonged PT and aPTT) as well as increased fibrinolysis (eg, elevated FDPs and D-dimer). But similar presentation in any patient began on heparin therapy within the preceding 5 to 10 days, should raise the possibility of heparin-induced thrombocytopenia (HIT).]]
Answer E	AnswerE::Sub therapeutic anti-coagulation
Answer E Explanation	AnswerEExp::''' Incorrect ''' : Even though in this patient PT/INR are subtherpeutic, the PTT is therapeutic and hence properly anti-coagulated.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy and is usually referred to immune mediated phenomenon. There are two types of HIT, type I and type II. Type I HIT patients characteristically have a transient decrease in platelet count (rarely <100,000) without any further symptoms and can recover even if heparin is continued to be administered. It occurs in 10-20% of all patients on heparin and is not due to an immune reaction and antibodies are not found upon investigation. HIT-1 is due to heparin-induced platelet clumping; it is innocuous. Type II is due to an autoimmune reaction with antibodies formed against platelet factor 4 (PF4), neutrophil-activating peptide 2 (NAP-2) and interleukin 8 (IL8) which form complexes with heparin. The major clinical problem associated with HIT is thrombosis, both venous and arterial. The precise mechanism of this hypercoagulable state is unknown, although the release of pro-coagulants from activated platelets along with endothelial cell activation and endothelial cell injury has been postulated as a primary event. If a patient on heparin develops an initial or recurrent thrombotic event, along with the presence of thrombocytopenia, it is due to HIT rather than failure of anticoagulation. The major manifestations of venous thrombosis are deep vein thrombosis (DVT) and pulmonary embolism. Other manifestations of venous thrombosis include venous limb gangrene and cerebral sinus thrombosis. Arterial thrombosis, although less common, can lead to a variety of clinical manifestations including stroke, myocardial infarction, acute limb ischemia from peripheral arterial occlusion, or organ infarction (mesentery, kidney). Educational Objective: References: ]]
Approved	Approved::Yes
Keyword	WBRKeyword::HIT, WBRKeyword::Heparin induced thrombocytopenia, WBRKeyword::DIC, WBRKeyword::Warfarin
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::