Platelet function disorders
- Lesion
Platelets can be present in normal numbers but fail to stick, clump or release their signals. Inherited and drug or kidney causes exist.
What it is
Qualitative platelet disorders cause mucocutaneous bleeding with normal or near-normal counts. Inherited forms teach the steps of the platelet plug: defective adhesion (Bernard–Soulier syndrome, lack of GPIb/IX, the vWF receptor), defective aggregation (Glanzmann thrombasthenia, lack of GPIIb/IIIa, the fibrinogen receptor) and defective secretion (storage-pool disorders). Acquired forms are much more common: aspirin and other NSAIDs inhibit cyclooxygenase and thromboxane A2, and uraemia impairs adhesion, secretion and aggregation.
Step by step
- Adhesion: GPIb/IX binds vWF on exposed subendothelium (lost in Bernard–Soulier and in vWD).
- Activation: platelets release ADP and synthesize thromboxane A2 (blocked by aspirin; weak in storage-pool disease).
- Aggregation: activated GPIIb/IIIa binds fibrinogen bridges between platelets (lost in Glanzmann).
- Any broken step leaves a weak primary plug and mucocutaneous bleeding.
Platelet function disorders
| Disorder | Defect | Step lost | Key test findings |
|---|---|---|---|
| Bernard–Soulier syndrome | GPIb/IX deficiency | Adhesion to vWF | Giant platelets, low count, no response to ristocetin |
| Glanzmann thrombasthenia | GPIIb/IIIa deficiency | Aggregation | Normal count and size, no aggregation with ADP or collagen, ristocetin normal |
| Storage-pool disorders | Few dense or α granules | Secretion and amplification | Weak second wave of aggregation |
| Aspirin and NSAIDs | Cyclooxygenase inhibition | Thromboxane A2 synthesis | Impaired aggregation with arachidonic acid |
| Uraemia | Toxins affecting several steps | Adhesion, secretion, aggregation | Normal count; improves with dialysis |
Clinical notes
- Easy bruising, nosebleeds, heavy menses and bleeding after dental work despite a normal platelet count.
- Wiskott–Aldrich syndrome combines small platelets, eczema and immunodeficiency.
Test yourself
Think of the answer, then tap the question to see it.
Which glycoprotein is missing in Glanzmann thrombasthenia?
GPIIb/IIIa, the fibrinogen receptor needed for aggregation.
Which platelet disorder shows giant platelets and no agglutination with ristocetin?
Bernard–Soulier syndrome (GPIb/IX deficiency).
How does aspirin impair platelet function?
It irreversibly inhibits cyclooxygenase, blocking thromboxane A2 synthesis for the life of the platelet.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Glanzmann thrombasthenia: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Bernard-Soulier syndrome: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.