A 9 year old boy with elevation in both PT and APTT. What is the diagnosis aEUR’
Correct Answer: Defect in common pathway
Description: Defect in common pathway Traditionally the blood coagulation pathway has been divided into extrinsic and intrinsic pathways, converging where factor X is activated. The role of both extrinsic and intrinsic pathways is to eventually produce prothrombin activator. Prothrombin activator is a complex of :- - Activated factor XQ - Activated factor V andQ --ca+-1-u . Both extrinsic and intrinsic pathways involve a number of clotting factors which paicipate in cascading reactions, that ultimately lead to the formation of activated factor X which combines with factor V and Ca++ to .form prothrombin activator. . When a blood vessel ruptures, clotting occurs by both pathways simultaneously. . Tissue thronzboplastin released from the damazed cells in the vascular endothelium activates extrinsic pathway, while, . Contact of factor XII and platelets with collagen in the vascular wall initiates the intrinsic pathway Thrombin Time . It is the time taken for clotting to occur when thrombin is added to the plasmaQ (normal < 15 s). . It tests the conversion of fibrinogen to fibrin and depends on adequate fibrinogen levels('. . So, the conditions in which fibrinogen level is decreased will cause prolonged thrombin time. These conditions are a) AfibrinogenemiaQ b)DysfibrinogenemaQ c) Heparin-like inhibitors or heparin administration('. d) Disseminated intravascular coagulation(' Paial Thromboplastin Time (PTT)(' . This test is used for measuring the integrity of the intrinsic(' and common pathways. . It measured the clotting time from factor XII to fibrin clot formation. . To perform PTT, patient's plasma is mixed with calcium and phospholipid_(paial thromboplastin), both of which arc required factor in coagulation cascade. . An intrinsic pathway activator such as silica or kaolin is mixed to activated the intrinsic pathway. Prothrombin Timedeg . The prothrombin time is a general measure of the integrity of extrinsic and common pathway('. . The PT measures the time .from factor VII activation to fibrin clot formation. . To perform PT a patients plasma is mixed with calcium and thromboplastin (Thromboplastin is a tissue extract that contains abundant phospholipid and tissue factor and therefore this mixture activates the factor VII). Bleeding time(' . It is the time taken for a standardized skin puncture to stop bleeding('. . It is not a test of coagulation rather it tests the ability of the vessels to vasoconstrictQ and the platelets to form a hemostatic plug. . h is believed that hemostasis in a small superficial wound such as that produced when measuring the bleeding time depends upon the rate at which a stable platelet plug is formed and thus provides a measure of the efficiency of the vascular and platelet phases; however, it does not discriminate between vascular defects, thrombocytopenia and platelet dysfunction.
Category:
Pathology
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