Platelet function disorders

Platelets are elements within the bloodstream that recognize and cling to damaged areas inside blood vessels. When they do this, the platelets trigger a series of chemical changes that result in the formation of a blood clot. Thereare certain hereditary disorders that affect platelet function and impair their ability to start the process of blood clot formation. One result is the possibility of excessive bleeding from minor injuries or menstrual flow.

Platelets are formed in the bone marrow a spongy tissue located inside the long bones of the body as fragments of a large precursor cell (a megakaryocyte). These fragments circulate in the bloodstream and form the first line of defense against blood escaping from injured blood vessels.

Damaged blood vessels release a chemical signal that increases the stickinessof platelets in the area of the injury. The sticky platelets adhere to the damaged area and gradually form a platelet plug. At the same time, the platelets release a series of chemical signals that prompt other factors in the blood to reinforce the platelet plug. Between the platelet and its reinforcements, a sturdy clot is created that acts as a patch while the damaged area heals.

There are several hereditary disorders characterized by some impairment of the platelet's action. Examples include von Willebrand's disease, Glanzmann's thrombasthenia, and Wiskott-Aldrich syndrome. Vulnerable aspects of platelet function include errors in the production of the platelets themselves or errors in the formation, storage, or release of their chemical signals. These defects can prevent platelets from responding to injuries or from prompting the action of other factors involved in clot formation.

Platelet function disorders can be inherited, but they may also occur as a symptom of acquired diseases or as a side effect of certain drugs, including aspirin. Common symptoms of platelet function disorders include bleeding from the nose, mouth, vagina, or anus; pinpoint bruises and purplish patches on theskin; and abnormally heavy menstrual bleeding.

In diagnosing platelet function disorders, specific tests are needed to determine whether the problem is caused by low numbers of platelets or impaired platelet function. A blood platelet count and bleeding time are common screening tests. If these tests confirm that the symptoms are due to impaired platelet function, further tests are done that pinpoint the exact nature of the defect.

Treatment is intended to prevent bleeding and stop it quickly when it occurs.For example, patients are advised to be careful when they brush their teethto reduce damage to the gums. They are also warned against taking medicationsthat interfere with platelet function. Some patients may require iron and folate supplements to counteract potential anemia. Platelet transfusions may benecessary to prevent life-threatening hemorrhaging in some cases. Bone marrow transplantation can cure certain disorders but also carries some serious risks. Hormone therapy is useful in treating heavy menstrual bleeding. Von Willebrand's disease can be treated with desmopressin (DDAVP, Stimate). The outcome depends on the specific disorder and the severity of its symptoms. Platelet function disorders range from life-threatening conditions to easily treatedor little-noticed problems.

Inherited platelet function disorders cannot be prevented except by genetic counseling; however, some acquired function disorders may be guarded against by avoiding substances that trigger the disorder.

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