Condensed Case

A 14-year-old girl had a tooth extracted and was noted to have unexpected bleeding following extraction. She bled for 24 hours before the bleeding could be stopped. The dentist recommended that she have a hematology evaluation for the unexpected bleeding. What questions concerning family history should be asked, and what baseline coagulation tests should be considered?

Answer

This patient is exhibiting signs of mucosal bleeding, the type of bleeding seen in platelet adhesion defects such as vWD and BSS. The family of the patient should be asked about the bleeding history of family members, such as umbilical cord bleeding, circumcision bleeding, bleeding from minor cuts and abrasions, or gum or nose bleeding. The patient's mother revealed that her sibling had serious bleeding after a tonsillectomy procedure. This fact points to an autosomal defect. Routine studies that should be ordered are bleeding time (platelet function assay), PT, and aPTT. Factor assay should be considered if the PT or PTT are prolonged.

Summary Points

• A normal platelet count is 150 to 450 X109/L.

• Decreased platelet counts will lead to mucosal membrane bleeding such as gingival bleeding, epistaxis, purpura, and petechiae.

• Preanalytic variables that may lead to thrombocy-topenia include improper mixing of tubes, improper anticoagulant used, and improper amount of sample collected.

• Acute idiopathic thrombocytopenia purpura is often a condition of children recovering from viral illness who show a dramatic drop in platelet count.

• Chronic idiopathic thrombocytopenia purpura occurs in adults as a result of an IgG antibody produced against platelets.

• Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are consumptive disorders of platelets.

• Individuals with TTP present with fever, a microan-giopathic hemolytic anemia, neurological complications, thrombocytopenia, and renal failure.

• Individuals with HUS are predominantly children, with fever, bloody diarrhea, microangiopathic hemolytic anemia, thrombocytopenia, and renal failure.

• von Willebrand's disease (vWD) is a disorder of platelet adhesion in which von Willebrand factor is decreased or absent.

vWD is the most common inherited qualitative platelet disorder, affecting 1% to 3% of the world's population.

There are three primary types of vWD: type 1, type 2A, and type 3.

Bernard Soulier syndrome is a platelet adhesion defect in which glycoprotein Ib is decreased or absent.

Glanzmann's thrombasthenia is a defect of platelet aggregation that shows an absence of glycoprotein IIb/IIIa.

Platelets from patients with vWD disease and Bernard Soulier syndrome will NOT aggregate with ristocetin.

Aspirin impairs platelet function by interfering with the synthesis of thromboxane A2, a potent platelet-aggregating agent.

The platelet release function is impaired in the inherited disorders: Chediak-Higashi, Hermansky-Pudlak, Wiskott-Aldrich, gray platelet syndrome, and thrombocytopenia with absent radii syndrome. External conditions that alter platelet function include drugs, paraproteinemias, uremia, and the use of plasma expanders, like dextran.

Skin, collagen, and blood vessels are essential elements in the hemostatic system. Any abnormality, inherited or acquired, in any one of these components of the vascular system will lead to mucosal bleeding such as purpura, petechiae, ecchymosis, or telangiectasia.

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