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Platelet Disorders

Platelets are small cells circulating in the blood, which play an important role in stopping bleeding and beginning the repair of injured blood vessels.

In platelet function disorders, a person’s blood platelets do not work properly. The result is that blood does not clot the way it should. When tissues are injured, damage to a blood vessel may result in leakage of blood through holes in the vessel wall. The vessels can break near the surface, as in a cut. Or they can break inside the body, making a bruise or an internal bleeding.

When a blood vessel is damaged, there are four stages in the normal formation of a clot.

  • Stage 1: The blood vessels is damaged and the bleedings starts.
  • Stage 2: The blood vessels constrict to slow the flow of blood to the injured area.
  • Stage 3: Platelets stick to, and spread on, the walls of damaged blood vessels. This is called platelet adhesion. These spreading platelets release substances that activate other nearby platelets which clump at the site of injury to form a platelet plug. This called platelet aggregation.
  • Stage 4: The surface of these activated platelets then provides a site for blood clotting to occur. Clotting proteins circulating in the blood are activated on the surface of the platelets to form a mesh-like fibrin clot. These proteins work like dominos, causing a chain reaction. This is called the coagulation cascade.

Platelet function disorders can affect clotting in several ways, depending on the type of disorder.

  • The platelets don’t stick to the vessel walls at the site of an injury.
  • The platelets don’t clump together (aggregate) to form a plug.
  • The platelets don’t activate blood proteins to form a solid fibrin clot.
Serious hereditary platelet function disorders are quite rare. However, because the majority of people have very mild symptoms, many cases are not diagnosed. Doctors do not know the exact number of people who have these disorders. Some think as many as 1 person in 100 has a platelet function disorder.

There are many kinds of platelet function disorders. They can be divided into two broad categories:

  • Hereditary disorders (meaning that they run in the family). Each family needs to be assessed individually to try to find out their inheritance pattern.
  • Acquired disorders (meaning they are caused by other diseases or the use of medications. A person can get an acquired platelet function disorder in two ways: from taking certain medication or as a result of another medical condition.

The hereditary disorders can be further divided according to how the platelets do or do not function:

  • Disorders of platelet adhesion (Bernard-Soulier Syndrome) in which platelets fail to stick and clump together at the site of the injury
  • Disorders of platelet aggregation (Glanzmann Thrombasthenia) in which platelets fail to form a plug at the site of an injury
  • Disorders of platelet secretion
  • Disorders of platelet procoagulant (Scott Syndrome)
  • Combined abnormalities of number and function (May-Hegglin Anomaly, Alport Syndrome and Wiskott-Aldrich Syndrome).
 Most people have mild symptoms. Many individuals have no symptoms at all unless they have a serious injury or an operation. In a few individuals, platelet function disorders can cause severe bleeding. Healthcare professionals should always be told about a person’s platelet function disorder before dental procedure or surgery.