• Diagnosis
• Treatment

Platelets are small cells that circulate in the blood. They are involved in the formation of blood clots and the repair of damaged blood vessels. When a blood vessel is injured, platelets stick to the damaged area and spread along the surface to stop the bleeding (this process is called adhesion). At the same time, chemical signals are released from small sacks inside the platelets called granules (this process is called secretion). These chemicals attract other platelets to the site of injury and make them clump together to form what is called a platelet plug (this process is called aggregation).

Sometimes the platelet plug is enough to stop the bleeding. However if the wound is large, other proteins called clotting factors are recruited to the site of injury. These clotting factors work together on the surface of the platelets to form and strengthen the blood clot.

There are many different types of inherited platelet disorders. In this section we will describe the more common disorders Bernard Soulier syndrome, Glanzmann thrombasthenia and storage pool deficiencies.

If the disorder you have been diagnosed with has not been described here please talk to your local haemophilia centre who will be able to give you more information as well as providing information sheets or useful links.

Bernard-Soulier syndrome

Bernard-Soulier syndrome is a platelet function disorder caused by an abnormality in the genes for glycoprotein Ib/IX/V. These genes code for a group of linked proteins normally found on the surface of platelets, the glycoprotein Ib/IX/V receptor (also called the Von Willebrand factor or VWF receptor). Because this receptor is absent or is not working properly, platelets do not stick to the injured blood vessel wall the way they should and it is difficult for the normal blood clot to form.

Bernard-Soulier syndrome is an autosomal recessive disorder, meaning that both parents must carry an abnormal gene (even though they themselves don’t have the disease) and pass that abnormal gene on to their child. Like all autosomal recessive disorders, it is found more frequently in areas of the world where marriage between close relatives is common. Bernard-Soulier syndrome affects both males and females.

Glanzmann thrombasthenia

Glanzmann thrombasthenia is a platelet function disorder that is caused by an abnormality in the genes for glycoproteins IIb/IIIa. These genes code for a group of linked proteins normally found on the surface of platelets, the glycoprotein IIb/IIIa receptor (also called the fibrinogen receptor). Because this receptor is absent or is not working properly, platelets do not stick to each other at the site of injury and it is difficult for the normal blood clot to form.

Glanzmann thrombasthenia is an autosomal recessive disorder, meaning that both parents must carry an abnormal gene (even though they themselves don’t have the disease) and pass that abnormal gene on to their child. Like all autosomal recessive disorders, it is found more frequently in areas of the world where marriage between close relatives is common. Glanzmann thrombasthenia affects both males and females.

Storage pool deficiencies

Storage pool deficiencies are a group of disorders caused by problems with platelet granules. Granules are little sacs inside the platelet in which proteins and other chemicals important to its function are stored. There are two types of granules: alpha granules and dense granules.

Some storage pool deficiencies are caused by a lack of granules, but the most common ones are caused by a failure of the platelets to empty the contents of the granules into the bloodstream (this is called the secretory or release mechanism).

• Release defects are a diverse group of disorders caused by a problem with the secretory mechanism. Even though the granules are present within the platelets, their contents are not emptied into the bloodstream properly.

• Delta storage pool deficiency is a platelet function disorder caused by a lack of dense granules and the chemicals normally stored inside them. Without these chemicals, platelets are not activated properly and the injured blood vessel does not constrict to help stop bleeding. This type of bleeding problem can be a feature of other inherited conditions (such as Hermansky-Pudlak syndrome and Chediak-Higashi syndrome).

• Grey platelet syndrome is a very rare platelet function disorder caused by a lack of alpha granules and the chemicals normally stored inside them. Without these proteins, platelets cannot stick to the blood vessel wall, clump together the way they should, or repair the injured blood vessel.

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