Chapter 3: Hemostasis and Thrombosis
A 26-year-old woman presents with a 3-month history of increasing fatigue, heavier than usual menstrual periods, and epistaxis. She had her wisdom teeth removed as a teenager with no complications. She has no family history of bleeding in the family and is currently on no prescribed or over-the-counter medications. On physical exam, her vitals, including temperature, pulse, blood pressure, and respiration, are normal. She has a petechial rash on her legs, as well as pale gingiva. Her laboratory tests reveal a normal WBC, PT, aPTT, and fibrinogen with a low hemoglobin but normal red blood cell morphology and a platelet count of 3000/µL (reference value 150,000–400,000/µL). What is the most likely diagnosis?
C. Drug-induced thrombocytopenia
Explanation: The patient has anemia (likely secondary to bleeding) and severe thrombocytopenia with onset as an adult (acquired condition). She is not acutely ill, which makes TTP and DIC less likely. Also, the peripheral blood smear shows normal red blood cell morphology (i.e., no schistocytes or microangiopathic hemolytic anemia), further excluding these. DIC would also show abnormal PT, aPTT, and fibrinogen, since it is a consumptive process. She is on no medications/drugs excluding drug-induced thrombocytopenia. She has no fever, lymphadenopathy, or splenomegaly, which might suggest a lymphoma. ITP is essentially a diagnosis of exclusion, and by excluding the others, it is the most likely diagnosis.
A 2-year-old boy presents with chronic epistaxis. His mother states that he is on no medication, prescribed or over the counter. She states that there is a family history of Glanzmann thrombasthenia. The boy has a normal CBC, PT, aPTT, fibrinogen, vWF antigen and activity. An LTA is performed. Which of the following is the most likely result?
A. Normal aggregation in response to all agonists
B. Normal agglutination in response to ristocetin; decreased to absent aggregation in response to thrombin, collagen, ADP, and arachidonic acid
C. Normal aggregation in response thrombin, collagen, ADP, and arachidonic acid; decreased agglutination in response to ristocetin
D. Normal aggregation/agglutination in response to thrombin, ADP, collagen, and ristocetin; decreased aggregation in response to arachidonic acid only
Explanation: The correct answer is B which is the typical pattern seen in this disorder with loss of integrin αIIbβ3 (fibrinogen receptor), which means that regardless of the agonist and activation of the platelet, he cannot aggregate. He clearly has a disorder of ...