Storage pool deficiencies

What are 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 can not stick to the blood vessel wall, clump together the way they should, or repair the injured blood vessel.

Symptoms
Symptoms of storage pool deficiencies vary from one individual to the next, but they are usually mild to moderate.
 
People with storage pool deficiencies may experience:

  • Easy bruising
  • Nose bleeds
  • Bleeding from gums
  • Heavy or prolonged menstrual bleeding (menorrhagia) or bleeding after childbirth
  • Abnormal bleeding after surgery, circumcision, or dental work

Diagnosis
The diagnosis of storage pool deficiencies requires a careful medical history and a series of tests that should be performed by a specialist at a hemophilia treatment centre.

In people with storage pool deficiencies:

  • The bleeding time (a standardized test of the time it takes for a small cut to stop bleeding) is often longer than normal. This test may be difficult to perform in young children
  • Platelets do not clump together the way they should in special laboratory tests (platelet aggregation)
  • Granules may not be visible when platelets are looked at with an electron microscope

Treatment
Most people with storage pool deficiencies only need treatment during surgical procedures (including dental work) and after injury or trauma. When needed, storage pool deficiencies may be treated with:

  • Antifibrinolytic drugs
  • Desmopressin (may not be useful in alpha granule deficiency)
  • Platelet transfusions

People with inherited platelet disorders should not take Aspirin®, nonsteroidal anti-inflammatory drugs (such as ibuprofen and naproxen), and blood thinners, which can make their bleeding symptoms worse.

 

Updated May 2012

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