Platelet and Coagulation Disorders MCQs

Pathology · 68 free questions with answers & explanations.

1. A 30-year-old woman presents with recurrent mucosal bleeding, prolonged bleeding time, and a normal platelet count. Platelet aggregation studies show absent aggregation with ADP, collagen, epinephrine, and arachidonic acid, but normal aggregation with ristocetin. Which diagnosis is most consistent?
2. Heparin-induced thrombocytopenia (HIT) type II is a prothrombotic disorder caused by IgG antibodies against which antigen complex, leading to paradoxical thrombosis despite low platelet count?
3. A 30-year-old woman is 28 weeks pregnant and develops thrombocytopenia (platelets 45,000/µL), microangiopathic hemolytic anemia, and fever. Serum ADAMTS13 activity is <10% with a high-titer inhibitor. Which diagnosis is confirmed and what is the immediate treatment?
4. A 40-year-old man with deep vein thrombosis is found to have an abnormal platelet aggregation test: normal aggregation with ADP, collagen, epinephrine, and ristocetin, but ABSENT aggregation with ristocetin corrected by adding normal plasma. He has a mild bleeding history. Which condition is diagnosed?
5. Thrombotic thrombocytopenic purpura (TTP) is distinguished from hemolytic uremic syndrome (HUS) clinically and mechanistically. The pathogenesis of idiopathic (acquired) TTP involves:
6. In disseminated intravascular coagulation (DIC), both thrombosis and bleeding occur simultaneously. The fibrinolytic inhibitor PAI-1 (plasminogen activator inhibitor type 1) paradoxically contributes to the coagulopathy by:
7. A patient with TTP has ADAMTS13 activity <10% due to an autoantibody against ADAMTS13. ADAMTS13 normally cleaves von Willebrand factor at which specific site, and what is the consequence of its deficiency?
8. A neonate develops hemorrhage on day 3 of life. PT and aPTT are both prolonged, platelet count is normal, fibrinogen is normal, and there is no family history. Mixing studies correct both PT and aPTT. The diagnosis is:
9. Thrombotic thrombocytopenic purpura (TTP) results from deficiency of ADAMTS13. ADAMTS13 normally cleaves which substrate, and at which site?
10. In heparin-induced thrombocytopenia type 2 (HIT-2), the mechanism of platelet activation and paradoxical thrombosis involves:
11. A 25-year-old woman develops thrombocytopenia, microangiopathic hemolytic anemia (MAHA), neurological symptoms, and fever 5 days after starting clopidogrel. Peripheral smear shows schistocytes. ADAMTS13 activity is severely reduced (<10%). The pathomechanism involves:
12. A newborn male develops intracranial hemorrhage after a circumcision. PT is markedly prolonged, aPTT is normal, platelet count and bleeding time are normal. Factor assay shows isolated Factor VII deficiency. The most likely inheritance pattern is:
13. A patient with thrombotic thrombocytopenic purpura (TTP) has ADAMTS13 activity <10% of normal. ADAMTS13 normally cleaves which substrate?
14. Heparin-induced thrombocytopenia (HIT) type II is paradoxically prothrombotic despite thrombocytopenia. The mechanism involves:
15. A 30-year-old woman has isolated prolonged bleeding time with normal platelet count, normal PT, and normal aPTT. Platelet aggregation studies show absent aggregation with ADP, collagen, and epinephrine but normal aggregation with ristocetin. Flow cytometry reveals absent GPIIb (CD41) and GPIIIa (CD61). This is:
16. A patient develops thrombocytopenia 8 days after starting unfractionated heparin for DVT treatment. Platelet count dropped from 180,000 to 55,000/µL. New thrombus detected in the arm. ELISA for anti-PF4/heparin IgG is strongly positive (OD 2.4). Functional serotonin release assay (SRA) is positive. The pathogenesis of HIT Type 2 involves IgG antibodies binding PF4-heparin complexes and activating platelets through which receptor?
17. Thrombotic thrombocytopenic purpura (TTP) is caused by deficiency of ADAMTS13. The substrate of ADAMTS13 and the mechanism of thrombosis are:
18. Disseminated intravascular coagulation (DIC) in obstetric complications involves tissue factor (TF) release. Which obstetric condition is most commonly associated with acute fulminant DIC through massive TF release?
19. A 25-year-old woman with inherited severe von Willebrand disease type 3 is being evaluated for surgery. Her ADAMTS13 level is normal. In which molecular step of primary hemostasis does von Willebrand factor deficiency most critically impair platelet function at sites of high shear stress?
20. Heparin-induced thrombocytopenia type II (HIT II) is a prothrombotic, immune-mediated complication of heparin. What is the molecular target of pathogenic HIT antibodies, and why does thrombocytopenia paradoxically coexist with thrombosis rather than bleeding?
21. A 28-year-old woman presents with thrombocytopenia, haemolytic anaemia (schistocytes on smear), fever, neurological symptoms, and renal failure. ADAMTS13 activity is <10%. This finding indicates that thrombotic thrombocytopenic purpura (TTP) in this patient is driven by:
22. A 30-year-old woman develops thrombocytopenia and microangiopathic haemolytic anaemia 5 days after starting ticlopidine. ADAMTS13 activity is <10% of normal. Which mechanism is primarily responsible for this complication?
23. A patient with haemophilia A has a factor VIII inhibitor titre of 50 Bethesda units (BU). Which therapeutic strategy is indicated for acute bleeding in high-responder haemophilia A with inhibitors?
24. A 30-year-old woman develops thrombocytopenia and microangiopathic hemolytic anemia (MAHA) 5 days after starting a heparin infusion for DVT. Her platelet count drops from 220,000 to 45,000/μL. The 4T score is 6 (high probability). Which antibody-mediated mechanism underlies heparin-induced thrombocytopenia (HIT), and why does it cause thrombosis rather than simply thrombocytopenia?
25. A 28-year-old woman develops severe thrombocytopenia 5 days after initiating unfractionated heparin therapy for deep vein thrombosis. Her platelet count falls from 210,000 to 42,000/μL. She develops a new arterial thrombus in the left popliteal artery. The 4T score pre-test probability is high. The pathomechanism of heparin-induced thrombocytopenia type II (HIT) is:
26. A patient with thrombocytopenia, microangiopathic hemolytic anemia (MAHA), renal failure, and neurological symptoms is diagnosed with thrombotic thrombocytopenic purpura (TTP). The molecular defect in acquired TTP and its direct pathophysiological consequence is:
27. A 35-year-old woman presents with thrombocytopenia, microangiopathic hemolytic anemia (MAHA), neurological symptoms, fever, and renal impairment (pentad). ADAMTS13 activity is <5% and ADAMTS13 inhibitor is positive. What is the pathomechanism of this condition?
28. A patient undergoes heparin therapy and develops thrombocytopenia on day 8. Serotonin release assay (SRA) is positive. The pathogenesis of heparin-induced thrombocytopenia type II (HIT) involves:
29. A 35-year-old woman develops thrombocytopenia and microangiopathic hemolytic anemia 5 days after initiating heparin therapy. ELISA is positive for anti-PF4/heparin antibodies. What is the pathomechanism of thrombosis (paradoxical thrombosis with thrombocytopenia) in heparin-induced thrombocytopenia type II (HIT)?
30. In disseminated intravascular coagulation (DIC), which laboratory pattern distinguishes acute (decompensated) DIC from chronic (compensated) DIC, such as that seen in giant hemangioma (Kasabach-Merritt phenomenon)?
31. In immune thrombocytopenic purpura (ITP), platelets are destroyed by autoantibodies targeting which platelet surface glycoproteins?
32. A 25-year-old woman has recurrent mucocutaneous bleeding. Platelet count is normal. Bleeding time is prolonged. PT and aPTT are normal. Platelet aggregation studies show normal aggregation with ADP and collagen but absent aggregation with ristocetin. Von Willebrand factor antigen level is normal. What is the diagnosis?
33. A 5-year-old boy presents with hemarthroses and prolonged aPTT. PT and bleeding time are normal. Factor VIII activity is 1%. Which inheritance pattern applies and what distinguishes this from hemophilia B?
34. A 35-year-old woman presents with sudden severe thrombocytopenia, microangiopathic haemolytic anaemia, neurological symptoms, renal impairment, and fever. ADAMTS13 activity is <10%. This is thrombotic thrombocytopenic purpura (TTP). ADAMTS13 deficiency leads to accumulation of which substrate?
35. Heparin-induced thrombocytopenia type II (HIT) is a prothrombotic paradox. The pathogenesis involves IgG antibodies against platelet factor 4–heparin complexes. These IgG antibodies cause thrombocytopenia and thrombosis by which mechanism?
36. A 30-year-old woman has recurrent thrombocytopenia during each pregnancy. Labs show low platelets, fragmented red cells (schistocytes), elevated LDH, low haptoglobin, and normal coagulation studies. The MOST likely diagnosis is:
37. In hemophilia A, the deficient factor is Factor VIII. This factor normally acts as a cofactor for which enzyme in the intrinsic coagulation pathway?
38. A 30-year-old woman with SLE develops thrombocytopenia and the laboratory shows prolonged aPTT that does NOT correct on 1:1 mixing with normal plasma, anti-β2-glycoprotein I antibodies, and lupus anticoagulant. The most likely haematological complication she is at risk for is:
39. Bernard-Soulier syndrome is characterised by large platelets, thrombocytopenia, and absent platelet agglutination with ristocetin. The deficient platelet surface glycoprotein is:
40. In heparin-induced thrombocytopenia (HIT), the pathogenic antibody targets which antigen on platelet-factor 4 complexes?
41. A patient with haemophilia A has factor VIII activity at 2%. The level that corresponds to severe haemophilia with spontaneous haemarthroses is:
42. In heparin-induced thrombocytopenia (HIT type II), thrombocytopenia occurs due to:
43. Thrombotic thrombocytopenic purpura (TTP) is caused by deficiency of which enzyme, leading to accumulation of ultra-large von Willebrand factor multimers?
44. A 30-year-old woman presents with purpura, microangiopathic hemolytic anemia, thrombocytopenia, fever, and neurological symptoms. Peripheral smear shows schistocytes. ADAMTS13 activity is less than 5%. The diagnosis is:
45. A 35-year-old woman develops painful blue toes and digital ischemia after starting heparin for DVT treatment. Platelet count falls from 280,000 to 55,000/µL over 5 days. The mechanism of this complication is:
46. Bernard-Soulier syndrome is a hereditary bleeding disorder caused by deficiency or dysfunction of which platelet glycoprotein complex?
47. Heparin-induced thrombocytopenia type 2 (HIT) is a prothrombotic complication mediated by antibodies against which antigen?
48. A patient with TTP (thrombotic thrombocytopenic purpura) has microangiopathic hemolytic anemia and thrombocytopenia due to platelet-rich thrombi in microvessels. The fundamental pathogenesis involves:
49. A patient with TTP (thrombotic thrombocytopenic purpura) has a severe deficiency of ADAMTS13. Which mechanism directly causes thrombocytopenia and microangiopathic hemolytic anemia?
50. A 35-year-old woman with SLE has recurrent arterial and venous thromboses, three second-trimester pregnancy losses, and a prolonged aPTT that does not correct on mixing study. The diagnosis and pathogenic mechanism are:
51. A 5-year-old boy has prolonged bleeding time, normal platelet count, and absent platelet aggregation to ALL agonists (ADP, collagen, thrombin) except ristocetin. This is diagnostic of:
52. A 30-year-old woman presents with thrombocytopenia, microangiopathic hemolytic anemia, and neurological symptoms (confusion, seizures). Renal function is relatively preserved. LDH is markedly elevated; direct Coombs test is negative. What is the deficient or defective factor in the most common form of this condition?
53. In disseminated intravascular coagulation (DIC), why does the patient paradoxically develop both thrombosis and hemorrhage simultaneously?
54. A 30-year-old woman has thrombocytopenia, microangiopathic hemolytic anemia (schistocytes), fever, neurological symptoms, and renal impairment. The pathological mechanism involves:
55. Von Willebrand disease type 2B is characterised by a gain-of-function mutation in vWF that causes it to bind platelet GPIb spontaneously. The expected laboratory findings include:
56. A 30-year-old woman develops thrombocytopenia 5 days after starting unfractionated heparin for DVT prophylaxis. Platelet count drops from 220 × 10⁹/L to 55 × 10⁹/L. A new iliac vein thrombus is detected. Serotonin release assay is positive. The pathophysiology involves:
57. Von Willebrand factor (vWF) serves two main functions in hemostasis. Which of the following correctly describes BOTH functions?
58. Thrombotic thrombocytopenic purpura (TTP) is caused by deficiency of ADAMTS13, a metalloprotease. What is the substrate of ADAMTS13 and how does its deficiency lead to TTP?
59. Bernard-Soulier syndrome is a rare platelet disorder presenting with severe thrombocytopenia (with giant platelets) and mucocutaneous bleeding. The defective glycoprotein complex in Bernard-Soulier syndrome is:
60. Thrombotic thrombocytopenic purpura (TTP) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ dysfunction. The primary pathogenetic mechanism is:
61. Hemophilia A (factor VIII deficiency) results in a prolonged aPTT with normal PT. This pattern is explained by the fact that factor VIII participates in:
62. A 28-year-old woman presents with mucosal bleeding, petechiae, and thrombocytopenia following a viral illness. Peripheral smear shows large platelets. Bone marrow biopsy reveals increased megakaryocytes. Anti-platelet antibodies (IgG) directed against GPIIb/IIIa are detected. Which mechanism explains the thrombocytopenia?
63. A patient with thrombotic thrombocytopenic purpura (TTP) shows the classic pentad of features. The underlying pathogenesis involves deficiency or inhibition of which enzyme?
64. In disseminated intravascular coagulation (DIC), both bleeding and thrombosis occur simultaneously. Which of the following laboratory patterns is characteristic of consumptive coagulopathy in DIC?
65. Heparin-induced thrombocytopenia (HIT) is paradoxically associated with thrombosis despite thrombocytopenia. The pathophysiology involves:
66. Glanzmann thrombasthenia is a quantitative or qualitative deficiency of platelet glycoprotein IIb/IIIa (GPIIb/IIIa, integrin alphaIIbbeta3). The primary function of GPIIb/IIIa after platelet activation is:
67. Disseminated intravascular coagulation (DIC) presents with simultaneous thrombosis and haemorrhage. Which laboratory profile is MOST consistent with acute DIC?
68. Disseminated intravascular coagulation (DIC) results in a paradoxical combination of thrombosis and bleeding. The primary driver of coagulopathy in acute DIC is: