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Genetic disorder characterized by giant platelets, mild-to-moderate thrombocytopenia, abnormal platelet function, and bleeding disproportionate to the reduced number of platelets.

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Giant Platelet Syndrome; Familial Macrothrombocytopenia; Deficiency of Platelet Glycoprotein Ib; Hemorrhagiparous Thrombocytic Dystrophy.

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First described in 1948 by Jean Bernard and Jean-Pierre Soulier, French hematologists.

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Probably less than 1:1,000,000 in the general population.

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Autosomal recessive. Genetic research located the GP-1BA gene on 17pter-p12 for the classic Bernard-Soulier syndrome (type A) and the GP-1BB gene on 22q11.2 for type B.

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The mutation results in a deficiency of platelet membrane glycoprotein (GP) Ib (GP-1BA), GP-Is (glycocalicin), GP-V, and GP-IX. (Glycocalicin results from proteolytic cleavage of GP-1BA.) These factors are responsible for the interaction between von Willebrand factor and the platelet membrane and are essential for normal platelet adhesion in the early phase of primary hemostasis. Furthermore, the giant platelets show altered binding of factors V and XI and do not develop regular coagulation activity upon contact with collagen.

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Bleeding tendency noted during childhood. Clinical picture and morphologic features of the platelets on blood smear examination, which shows increased size (giant platelets may have a diameter up to 8 μm) with dense granulomeres, resulting in a pseudonucleated or lymphocytoid aspect.

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Moderate-to-severe bleeding of purpuric type (bruising, epistaxis, menorrhagia). Bleeding time is prolonged, but clot retraction and platelet aggregation by adenosine diphosphate and collagen are normal. Heterozygous family members may show approximately half the normal levels of platelet GP Ib-IX-V expression; however, they suffer from only mild bleeding diatheses, if at all. Affected patients have a history of frequent episodes of epistaxis, gingival and cutaneous bleeding, and hemorrhage associated with trauma. Platelet counts may range from very low (<30,000/μL) to marginally low or normal (∼200,000/μL). In individual patients it may fluctuate considerably over a period of years. Skin bleeding time may range from only marginally prolonged (5-10 minutes) to more than 20 minutes. The severity of symptoms may progressively worsen or become alleviated throughout puberty and adult life. Splenectomy apparently has been beneficial in moderating thrombocytopenia and the severity of clinical symptoms.

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Check platelet count and bleeding time. Bleeding tendency is variable (some patients remain asymptomatic until later adulthood), but can be severe during surgery, trauma, or pregnancy. Evaluate hematologic status (complete blood count, bleeding time, platelet function tests, prothrombin time, partial thromboplastin time). Activated recombinant factor VII (rFVIIa) and fresh plasma concentrate should be immediately available in the event they are required.

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Avoid central neuraxial blocks. Direct laryngoscopy and tracheal intubation must be atraumatic. General supportive measures and specific treatment of bleeding episodes. Severe hemorrhagic shock occurs spontaneously or secondary to surgery. High-dose recombinant factor VIIa has been used to correct bleeding and was postulated to act on platelets in the absence of tissue factor to activate factors IX and X and thus enhance thrombin generation. Transfusion of platelet-rich plasma is another technique that has been used successfully to stop severe hemorrhage.

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Consider use of desmopressin acetate (DDAVP) and antifibrinolytics. Avoid drugs or products adversely affecting platelet function, such as nonsteroidal antiinflammatory drugs and hydroethyl starch. Halothane and sevoflurane (and dibucaine) may affect platelet function. Antifibrinolytics may or may not be beneficial.

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Thrombopathic Thrombocytopenia: Although this disorder is similar ...

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