Platelet Function Disorders

How platelets work

When a blood vessel is injured, platelets:

1. Adhere to the damaged wall, using von Willebrand factor and receptors such as glycoprotein Ib
2. Activate, changing shape and releasing chemicals from internal granules
3. Aggregate, sticking to each other through glycoprotein IIb/IIIa and fibrinogen, forming a plug

A defect at any step causes a platelet function disorder, even if the platelet count is normal. A low count is a different problem (thrombocytopenia).

Causes

Acquired (common)

Inherited (rare)

• Storage pool and release disorders: the most common inherited group; usually mild bleeding
• Glanzmann thrombasthenia: absent or faulty glycoprotein IIb/IIIa; platelets cannot aggregate; moderate to severe bleeding
• Bernard-Soulier syndrome: missing glycoprotein Ib; large platelets and often low count
• Gray platelet syndrome, Hermansky-Pudlak syndrome (with albinism), Wiskott-Aldrich syndrome and others

Von Willebrand disease, the most common inherited bleeding disorder, affects platelet adhesion through von Willebrand factor and causes similar symptoms, so it is tested for at the same time.

Symptoms

Platelet disorders mainly cause mucocutaneous bleeding:

• easy bruising
• tiny red or purple spots (petechiae)
• nosebleeds
• bleeding gums
• heavy menstrual bleeding, often from the first period
• prolonged bleeding after cuts, dental extractions, surgery or childbirth
• gastrointestinal bleeding in some

Deep muscle and joint bleeds, typical of hemophilia, are uncommon.

Diagnosis

• Bleeding history, often using a standardized bleeding score
• Medication review, including over-the-counter drugs and supplements
• Complete blood count and blood smear: platelet number and size
• Clotting tests (PT, aPTT): usually normal
• Von Willebrand factor tests
• Platelet function analyzer (PFA-100) as a screening test
• Light transmission aggregometry: the main specialist test measuring how platelets respond to various activators
• Flow cytometry for glycoprotein defects
• Electron microscopy for granule defects
• Genetic testing for inherited disorders

Testing should be done off aspirin and NSAIDs for 7 to 10 days when safe.

Treatment

• Stop or avoid aspirin, NSAIDs and other drugs that affect platelets when possible; use acetaminophen for pain
• Desmopressin (DDAVP): releases von Willebrand factor and helps many mild inherited platelet disorders and uremic bleeding
• Tranexamic acid: an antifibrinolytic for nosebleeds, dental procedures and heavy periods
• Hormonal treatments for heavy periods: combined contraception, hormonal IUD
• Platelet transfusions for severe bleeding or major surgery, especially in Glanzmann thrombasthenia and Bernard-Soulier syndrome
• Recombinant activated factor VII for Glanzmann thrombasthenia with antibodies to platelets
• Iron supplements for anemia from blood loss
• Dialysis improves uremic platelet dysfunction
• Stem cell transplant for selected severe inherited disorders

Living with a platelet function disorder

• Tell all doctors and dentists before procedures
• Wear a medical alert ID if the disorder is significant
• Plan surgery and childbirth with a hematologist
• Use a soft toothbrush and maintain dental health to reduce gum bleeding
• Avoid contact sports if bleeding is severe

Frequently asked questions

Can you have a bleeding disorder with a normal platelet count?

Yes. In platelet function disorders, platelet numbers are normal or near normal but the platelets do not work properly. Von Willebrand disease also causes bleeding with a normal count. Specialized platelet function tests are needed to diagnose these.

What are the symptoms of a platelet function disorder?

Common symptoms are easy bruising, frequent or prolonged nosebleeds, bleeding gums, heavy menstrual periods and excessive bleeding after dental work, surgery or childbirth. Bleeding into joints or muscles is uncommon.

Does aspirin cause platelet dysfunction?

Yes. Aspirin permanently blocks a key enzyme in platelets, reducing their ability to clump for the rest of their 7 to 10 day lifespan. This is useful for heart protection but increases bleeding risk. NSAIDs have a shorter, reversible effect.

How are inherited platelet disorders treated?

Mild disorders often need treatment only for procedures or bleeding, using desmopressin or tranexamic acid. Severe disorders such as Glanzmann thrombasthenia may need platelet transfusions. Hormonal treatment helps heavy periods. A hematologist plans care.