Clinical Pathology: Hematology & Coagulation

• Inherited platelet disorders characterized by disorders of receptors and signal transduction include the following:

    Platelet cyclooxygenase deficiency

    Thromboxane (Tx) synthase deficiency

    TxA2 receptor defect

    Adenosine diphosphate (ADP) receptor defect (P2Y12)

• In general, patients with this class of defects present with abnormal primary hemostasis manifested by mild bleeding. Platelet number and morphology are usually normal.

• Tx synthase deficiency or a defect in the TxA2 receptor presents with an aspirin-like defect, but a thorough medication history will not show any ingestion of aspirin or aspirin-containing medications.

• There is marked impairment of platelet aggregation in response to arachidonic acid; aggregation with ADP and collagen are also reduced. Aggregation with Tx analogs and ristocetin are normal.

• These cases are diagnosed when there is an abnormal secondary wave of aggregation, but there are normal dense granules on electron microscopy and an absence of aspirin ingestion.

Bolton-Maggs PH, Chalmers EA, Collins PW, et al: A review of inherited platelet disorders with guidelines for their management on behalf of the UKHCDO. Br J Haematol 2006;135:603–633.

D’Andrea G, Chetta M, Margaglione M: Inherited platelet disorders: thrombocytopenias and thrombocytopathies. Blood Transf 2009;7:278–292.

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