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INTRODUCTION

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Abnormalities of platelet function are expressed primarily by mucocutaneous bleeding. The most frequent laboratory abnormality is abnormal platelet aggregation or prolongation of the closure time in an automated platelet function analyzer. The clinical value of the bleeding time is questionable because of lack of reproducibility and poor correlation with clinical bleeding and should not be used.

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  • Hereditary qualitative platelet disorders classified according to the responsible abnormalities are presented in Table 75–1.

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Table Graphic Jump Location
TABLE 75–1INHERITED DISORDERS OF PLATELET FUNCTION
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ABNORMAL GLYCOPROTEIN (GP) IIB/IIIA (INTEGRIN AIIBB3, CD41/CD61): GLANZMANN THROMBASTHENIA

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  • Glanzmann thrombasthenia is characterized by severely reduced or absent platelet aggregation in response to many physiologic agonists because of abnormalities of platelet GP IIb and/or IIIa (see Table 75–1).

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Etiology and Pathogenesis

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  • GPIIb/IIIa functions as receptor for fibrinogen and other adhesive glycoproteins.

  • It is required for platelet aggregation induced by all agonists believed to function in vivo.

  • Both GPIIb and GPIIIa are required for normal function, and defects in either component may cause thrombasthenia.

  • Many different molecular biologic abnormalities have been described that affect expression or various functions of the two molecules.

  • Inheritance of the disorder is autosomal recessive, but about 40% of patients are compound heterozygotes rather than homozygotes.

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Clinical Features

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  • The most frequent bleeding symptoms in patients with Glanzmann thrombasthenia are menorrhagia, easy bruising, epistaxis, and gingival bleeding.

  • Clinical expression ...

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