A 9 year old boy with elevation in both PT and APTT. What is the diagnosis aEUR'
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.
Defect in extrinsic pathway
Detect in intrinsic pathway
Platelet function defect
Defect in common pathway