Match each patient's clinical presentation and laboratory profile of abnormal hemostasis with the primary pathophysiologic mechanism responsible for their condition.
- A 4-year-old child with recurrent epistaxis and a normal platelet count. Aggregation studies show a normal response to ristocetin but absent responses to ADP, collagen, and epinephrine.Deficiency or dysfunction of the glycoprotein IIb/IIIa receptor complex, impairing platelet aggregation.
- A 16-year-old girl with heavy menses. Labs show mild thrombocytopenia and giant platelets. Platelet agglutination with ristocetin is absent and does not correct with the addition of normal plasma.Deficiency or dysfunction of the glycoprotein Ib-IX-V receptor complex, impairing platelet adhesion.
- A 5-year-old boy with the sudden onset of diffuse petechiae two weeks after a mild upper respiratory infection. Labs show an isolated profound thrombocytopenia with normal coagulation times.Production of autoantibodies against platelet surface glycoproteins leading to accelerated clearance by tissue macrophages.
- A 65-year-old hospitalized patient who develops a deep vein thrombosis and a 60% decline in platelet count seven days after starting subcutaneous venous thromboembolism prophylaxis.Development of antibodies against macromolecular complexes on the platelet surface, triggering widespread cellular activation and thrombosis.
Cevap
The child with normal ristocetin but absent ADP/collagen responses matches with the GP IIb/IIIa defect (Glanzmann thrombasthenia). The teenager with giant platelets and absent ristocetin agglutination that does not correct matches with the GP Ib defect (Bernard-Soulier syndrome). The child with post-viral isolated thrombocytopenia matches with autoantibody-mediated clearance (Immune Thrombocytopenia). The adult with delayed thrombocytopenia and thrombosis following prophylaxis matches with antibodies against macromolecular surface complexes (Heparin-Induced Thrombocytopenia).
Each clinical scenario corresponds uniquely to a distinct mechanism of primary hemostatic failure. Glanzmann thrombasthenia involves a GP IIb/IIIa deficiency causing failure of platelet aggregation. Bernard-Soulier syndrome involves a GP Ib deficiency leading to macrothrombocytopenia and failure of vWF-mediated adhesion. ITP involves splenic macrophage destruction of antibody-coated platelets. HIT involves PF4-heparin immune complexes causing paradoxical platelet activation and thrombosis.
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Anahtar Kavram
Qualitative and quantitative platelet disorders can be differentiated by their clinical context, peripheral smear findings, and specific responses to platelet aggregation studies.
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