Question 1

Aspirin affects platelet aggregation because it interferes with:

Accepted Answer

Aspirin inhibits cyclooxygenase activity, which is necessary for the synthesis of thromboxane A2, a potent inducer of platelet aggregation. This results in reduced platelet aggregation and decreased risk of blood clot formation.

Question 2

A patient's peripheral blood smear reveals many giant platelets. All platelet function tests show normal aggregation with the exception of ristocetin. From what is the patient most likely suffering?

Accepted Answer

The giant platelets and abnormal ristocetin-induced platelet aggregation suggest a problem with the platelet glycoprotein Ib-IX-V complex, which is responsible for binding to von Willebrand factor. Bernard-Soulier syndrome is a rare inherited disorder characterized by a deficiency or dysfunction of this complex, leading to impaired platelet adhesion and clot formation. Glanzmann's thrombasthenia is a rare inherited disorder characterized by a deficiency of the platelet glycoprotein IIb/IIIa complex, leading to impaired platelet aggregation. Storage pool disease is a collective term for a group of inherited disorders characterized by defects in granules that store various substances important for platelet function. Wiskott-Aldrich syndrome is a rare X-linked disorder characterized by a triad of thrombocytopenia, eczema, and recurrent infections, and is caused by mutations in the WAS gene.

Question 3

What laboratory tests are used to assess disorders of primary hemostasis and secondary hemostasis?

Accepted Answer

The answer of What laboratory tests are used to assess...

Question 4

How do hematologic disorders contribute to the pathogenesis of thrombocytopenia?

Accepted Answer

The answer of How do hematologic disorders contribute to the...

Question 5

What is the most common cause of thrombocytopenia?

Accepted Answer

Increased destruction is the most common cause of thrombocytopenia, which can occur in conditions such as immune thrombocytopenic purpura (ITP), drug-induced thrombocytopenia, and thrombotic microangiopathies.

Question 6

What would be the expected laboratory results in a patient with thrombocytopenia?

Accepted Answer

Thrombocytopenia is a condition characterized by low platelet counts, and a count of <50 x109/L is considered thrombocytopenic. The other laboratory results mentioned in options B, C, and D are more commonly associated with coagulation factor deficiencies rather than thrombocytopenia.

Question 7

Give at least five markers of differentiation between acute and chronic ITP.

Accepted Answer

The answer of Give at least five markers of differentiation...

Question 8

Immune complexes induce vasculitis by which of the following processes?

Accepted Answer

Immune complexes induce vasculitis primarily through the recruitment of neutrophils to the site where the immune complexes are deposited. These neutrophils, in an attempt to phagocytize the immune complexes, release enzymes and free oxygen radicals, which cause damage to the vessel wall, leading to vasculitis.

Question 9

Which of the following characteristics of chronic ITP differentiates it from acute ITP?

Accepted Answer

Chronic ITP often shows a gender predilection, with females being more commonly affected than males, typically at a ratio of about 3:1. This characteristic helps differentiate it from acute ITP, which does not have as strong a gender predilection. Acute ITP is more common in children and usually resolves within 6 months, whereas chronic ITP persists for longer than 12 months.

Question 10

What is a common etiology of ITP in children?

Accepted Answer

ITP (Immune Thrombocytopenic Purpura) in children is often preceded by a viral infection, such as chickenpox. This leads to an immune response that mistakenly targets and destroys platelets, resulting in the symptoms of ITP.

Question 11

Explain the pathophysiology of the following and why each typically has normal coagulation screening tests.
a. Bernard-Soulier syndrome
b. Glanzmann's thrombasthenia
c. δ-storage pool disease
d. Gray platelet syndrome

Accepted Answer

The answer of Explain the pathophysiology of the following and...

Question 12

a. Is it good practice to perform a bleeding time on a thrombocytopenic patient?
b. Why is a bleeding time not indicated to follow up on an abnormal PT or PTT?

Accepted Answer

The answer of a. Is it good practice to perform...

Question 13

A patient has a severe headache shortly before getting her blood tested. She takes a couple of aspirin and is scheduled for platelet aggregation studies. What effect will this have on the platelet aggregation studies?

Accepted Answer

Aspirin inhibits platelet aggregation by irreversibly inhibiting the enzyme cyclooxygenase, which leads to decreased production of thromboxane A2, a potent platelet aggregator. Therefore, platelets will show diminished activity with selected agonists in patients who have recently taken aspirin.

Question 14

A patient is known to be a chronic alcoholic. His blood is drawn, and his platelet count is 72 × 10⁹/L. What is the most likely reason for this occurrence?

Accepted Answer

Chronic alcohol consumption can lead to bone marrow suppression, including acquired hypoplasia of the bone marrow, which can result in decreased production of platelets.

Question 15

Describe the following and indicate whether they are typically seen in disorders of primary or secondary hemostasis.
a. Petechiae
b. Purpura
c. Ecchymoses
d. Hematomas

Accepted Answer

The answer of Describe the following and indicate whether they...

Question 16

Which of the following contributes to the pathogenesis of Bernard-Soulier syndrome?

Accepted Answer

Bernard-Soulier syndrome is a rare bleeding disorder caused by defects in the glycoprotein Ib/IX complex on the surface of platelets, which is important for platelet adhesion to von Willebrand factor and collagen. Abnormalities in glycoprotein IIb/IIIa are associated with Glanzmann thrombasthenia. High platelet count and low fibrinogen levels are not typically associated with Bernard-Soulier syndrome.

Quiz 33: Disorders of Primary Hemostasis