Compare and contrast Glanzmann thrombasthenia vs. Bernard-Soulier syndrome. Describe one similarity and one difference. Briefly explain how these two disorders can be distinguished by a confirmatory aggregation test.
The Correct Answer and Explanation is:
Glanzmann Thrombasthenia (GT) vs. Bernard-Soulier Syndrome (BSS)
Similarity:
Both Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) are inherited platelet disorders that result in bleeding tendencies. These conditions both affect the ability of platelets to aggregate properly, leading to increased bleeding, particularly in response to trauma or surgery.
Difference:
The primary difference between these two disorders lies in the specific defect in platelet function. Glanzmann thrombasthenia is caused by a deficiency or dysfunction of the glycoprotein IIb/IIIa complex, which is essential for platelet aggregation in response to fibrinogen. In contrast, Bernard-Soulier syndrome is caused by a deficiency or dysfunction of the glycoprotein Ib-IX-V complex, which serves as the receptor for von Willebrand factor (vWF) and is crucial for platelet adhesion to the vessel wall.
Distinguishing by Aggregation Test:
The confirmatory aggregation test can differentiate between these two conditions. In the Glanzmann thrombasthenia, platelets will show normal aggregation in response to ristocetin (which induces platelet aggregation via vWF), but they will fail to aggregate in response to other agonists like ADP, collagen, or thrombin due to the absence of the functional glycoprotein IIb/IIIa complex.
On the other hand, in Bernard-Soulier syndrome, platelets will fail to aggregate in response to ristocetin due to the defect in the glycoprotein Ib-IX-V complex, but they will aggregate normally in response to other agonists such as ADP or collagen.
By analyzing platelet aggregation patterns in response to various agonists, including ristocetin, one can distinguish between these two conditions.
