Disorders of platelet function
Some bleeding disorders are due to abnormalities of
platelet function rather than to a defect in platelet
number. Glanzmann's thrombasthenia, an inherited disorder
associated with a mildbleeding tendency, is due to a
deficiency of glycoprotein IIb–IIIa. Bernard-Soulier
syndrome, an inherited disorder associated with a pronounced
bleeding tendency, is due to a deficiency of glycoprotein
Ib on the platelet membrane. These platelets are unusually
large and morphologically bizarre. In the gray platelet
syndrome, the alpha granules are missing. Many other
platelet defects exist, but they have not been fully
characterized at a biochemical level.
The most common acquired disorder of platelet function
is associated with aspirin, or acetylsalicylic acid.
Aspirin reacts with platelets, even when the drug is
taken at low doses. This reaction impairs the ability
of platelets to produce a group of chemicals known as
prostaglandins. The inhibition of prostaglandin biosynthesis
and the decrease in the production of thromboxane A2
can be associated with a bleeding disorder. Other drugs
have asimilar effect, but aspirin is especially important
because of its wide use and the sensitivity of certain
persons to its action.
