What Are Platelet Function Disorders?

Platelet function disorders are a group of bleeding disorders where the platelets do not function appropriately, leading to bleeding. These disorders can be inherited (passed down in families) or acquired (developed at later time).  

Platelets are one part of our clotting system, the system that helps us stop bleeding. If your platelets don't function properly, you are at increased risk of bleeding. Symptoms may include:  

• Increased bruising
• Nosebleeds
• Gum bleeding
• Menorrhagia (excessive menstrual bleeding)
• Prolonged bleeding after a cut or other injury
• Prolonged bleeding with surgery

Platelet function disorders can be divided into two large categories: congenital (inherited) or acquired. The majority of the disorders are congenital, including:

• Glanzmann's thrombasthenia
• Bernard-Soulier syndrome
• Gray platelet syndrome
• MYH9-related disorders: May-Hegglin anomaly, Epstein syndrome, Fechtner syndrome, and Sebastian syndrome
• Wiskott-Aldrich syndrome: This is a syndrome of immunodeficiency and dysfunctional platelets. It is characterized by very small platelets (most platelet function disorders have normal to large platelets).  
• Chediak-Higashi syndrome
• Hermansky-Pudlak syndrome

Acquired causes include:

• Medications: Medications like aspirin, dipyridamole (Persantine), and clopidgrel (Plavix) are designed to reduce the function of platelets. Ibuprofen also decreases the effectiveness of platelets but less than aspirin.  
• Liver disease
• Uremia (severe renal disease)
• Myeloproliferative disorders like essential thrombocythemia

Opposed to other platelet disorders, which are often issues with the platelet number (elevated or decreased), platelet function disorders may have normal platelet counts.

Other types of platelet function disorders can have thrombocytopenia, or low platelet count. The platelets should be reviewed under the microscope on a peripheral blood smear. Several of the congenital platelet function disorders result in platelets that are larger than normal. Others are missing key components of the platelets, called granules, which can be seen. Sometimes the platelets are normal in appearance and size.  

The remaining work-up begins similarly to other bleeding disorders. Opposed to hemophilia (a disorder of coagulation factors), screening tests like prothrombin time (PT) and partial thromboplastin time (PTT) are normal. Diagnosing platelet function disorders require specialty testing. Below is a short list of commonly used tests.  

• Bleeding time: This test is not considered specific to platelet function disorders and because of test limitations is not considered an accurate test of the clotting system.  
• Platelet function assay: This is considered by many to be a good screening test for platelet disorders. This test is affected by the platelet count and may not be accurate if you have low platelet counts.  
• Platelet aggregation testing: This test looks at how well the platelets stick to one another (aggregation) in response to different stimuli. This test can also be used to measure the effectiveness of aspirin or clopidogrel (Plavix) therapy.  
• Platelet electron microscopy: This is a special way to look at platelets with a special microscope that can see the individual parts of the platelet.  

Treatment is based on the individual platelet function disorder you have. Some platelet function disorders rarely need treatment unless you are injured or require surgery.

• Aspirin and NSAIDs: Avoid aspirin or non-steroidal anti-inflammatory (NSAIDs) like ibuprofen. These medications reduce the function of platelets which may worsen the bleeding risk.
• Hormonal contraceptives: Similar to other causes of severe menstrual bleeding, hormonal contraceptives can be used to keep menstrual bleeding to a minimum.  
• Anti-fibrinolytic medications: Because it can be difficult for the body to make stable clots, particularly on the moist surfaces of the mucosa (mouth, nose, etc.), antifibrinolytic medications like Amicar or Lysteda may be used to stop bleeding. These medications are commonly used in these conditions for nosebleeds, gum bleeding, and menorrhagia. They can also be used after surgical procedures (particularly, mouth, nose, and throat) to prevent bleeding.  
• Platelet transfusions: Even in platelet function disorders with normal platelet counts, platelet transfusions may be used for severe bleeding or if you need to go to surgery.
• Factor VIIa (NovoSevenRT) infusion: This factor replacement product can be used in some patients with platelet function disorders. This is used mostly in patients that are unable to receive platelet transfusions as a treatment option.