bleeding tendency 2025 .pdf

Bleeding tendency Prof. Mohamed Moostafa LEARNING OBJECTIVES 1- To Know and understand the physiology of normal hemostasis 2- To Enumerate the causes of bleeding disorders in children 3- To have a systematized approach...

Bleeding tendency Prof. Mohamed Moostafa LEARNING OBJECTIVES 1- To Know and understand the physiology of normal hemostasis 2- To Enumerate the causes of bleeding disorders in children 3- To have a systematized approach for diagnosing child with bleeding 4- To Identify common bleeding disorders based on clinical and laboratory characteristics and know lines of managements NORMAL HEMOSTASIS PHASES OF HEMOSTASIS: - vasoconstriction - Endothelial injury and formation of the platelet plug; through: A) Platelet adhesion is by binding of platelet surface receptor GPIb to von Willebrand factor (VWF) in the subendothelium B) Platelet aggregation through binding GPIIb/IIIa receptor on the platelet surface to fibrinogen This mechanism is tested in vitro by platelet count, platelet function tests and VWF assay 1  N.B. Bleeding time is historically used for a long time as a diagnostic tool, but it is subjective, lacking sensitivity and specificity - Formation of fibrin clot by the coagulation cascade: a) The intrinsic pathway involves activation of factor IXa which in presence of VIIIa activates factor X. Tested in vitro by activated partial thromboplastin clotting time [aPTT]). b) The extrinsic pathway involves activation of VII (factor VIIa) which in presence of tissue factor activates factor X. tested in vitro by in vitro by prothrombin time [PT]). c) Common pathway: Both pathways converge on the activation of factor X which that converts prothrombin to thrombin. Thrombin converts fibrinogen from a soluble plasma protein into an insoluble fibrin clot (tested in the in vitro thrombin time [TT]). Eventually activated 13 convert unstable fibrin clot to stable clot - Removal of the clot by fibrinolysis. 2 3  DIFFERENTIAL DIAGNOSIS OF BLEEDING DISORDERS Vascular lesions: Usually produce palpable purpura - Hereditary: hereditary hemorrhagic telangiectasia (AD) - Acquired: a) Meningococcemia: life threatening emergency condition 4  b) IgA vasculitis (Henoch-Schönlein purpura) c) Other systemic CT diseases e.g., HHT, scurvy, corticosteroids, SLE, Platelet defects: Thrombocytopenia: Definition – Thrombocytopenia is defined as a platelet count