Congenital and Acquired Platelet Disorders: Current Dilemmas and Treatment Strategies

Platelets are important for primary hemostasis. When a blood vessel is damaged, platelets adhere to exposed subendothelial connective tissue and form a hemostatic plug. Formation of the plug is contingent upon a series of processes, with adhesion, activation, and aggregation all being involved. Patients with quantitative platelet disorders have reduced numbers of platelets. Patients with qualitative disorders have platelets that exhibit abnormal functioning. Defects that impair function can affect platelet receptors, secretory responses, or intracellular signaling pathways. Examples of qualitative platelet disorders include Glanzmann's thrombasthenia (GT) and Bernard-Soulier syndrome (BSS). The treatment of platelet disorders is primarily with platelet concentrates. However, in patients with abnormalities of their platelet surface receptors, platelet transfusion may provoke an immune response. Recombinant factor VIIa (rFVIIa) may provide hemostatically effective therapy in such patients.