Answer: b) Von Willebrand disease> Normal PT and aPTT rules out Hemophilia A> Glanzmann thrombasthenia and Bernard Soulier syndrome are qualitative platelet disordersPartial thromboplastin time (PTT)Prothrombin time (PT)Bleeding time (BT)* Tests intrinsic and common pathways of coagulation* Normal: 60 - 70 seconds* Tests extrinsic & common pathways* Normal 11-16 seconds* Normal 2-8 mins Prolonged aPTT (normal 30-40 s)Prolonged PTProlonged aPTT and PT* Deficiencies of factor 1, II, V, VIII, IX, X, XI, XII, Lupus anticoagulant* Heparin* | factors 1, II, V, VII, X* Vitamin K deficiency--early* Warfarin anticoagulation* | Factor II, V, X, or fibrinogen* Vitamin K deficiency--late* Direct thrombin inhibitorsLaboratory findings in Hemostatic disorders Coagulation disordersPlatelet disordersTESTHemophilia A & BvW DVit K |Liver failureITPTTPHepari nDICAspirinWarfari nBTN|N||||||NPlateletNNN||||-|NNPTNN||NNN|N|aPTT|N||NN||N|FDP-----+/--+--VON WILLEBRAND DISEASE* Most common inherited bleeding disorders of human* Type 1 - AD,. Most common type. Usually.* Type 2 - type 2A is AD, qualitative defects in vWF* Type 3 - AR. Extremely low levels of vWF. Severe clinical manifestations.Pathogenesis* vWF is synthesized by endothelial cells, platelets and megakaryocytes (a-granules) * Weibel-Palade bodies - glue factory of endothelial cells; synthesize> P-selectin - adhesion molecule for leukocytes> vWF - adhesion molecule for platelets* vWF is responsible for platelet adhesion (bridge between extracellular collagen matrix and platelet surface receptors)* GP Ib-IX is a major receptor for vWF* vWF acts as a carrier for factor VIII and important for its stability and prolongs half life* Factor VIII is synthesized normally but has 4, half-life due to deficiency of carrier moleculeType 1Type 2Type 3* Autosomal dominant* Due to missense mutation* Most common type* Reduced quantity of vWF* Mild to moderate bleeding* 2A - Autosomal dominant* Missense mutations* Qualitative defects of vWF* Mild to moderate* Autosomal recessive* Deletions or frame-shift mutations* Extremely low levels of vWF* Severe clinical manifestationsClinical features* Bleeding is uncommon in infancy and manifest in late childhood* The most common symptoms - sponatenous mucosal bleeding(e.g.epistaxis), excessive bleeding from wounds, menorrhagia* Frequently mild vWD manifests first during wisdom tooth extraction or tonsillectomy* Defects in platelet function despite normal platelet count* Acquired vWD is most commonly seen in MGUS; other conditions - multiple myeloma; Waldenstrom's macroglobulinemiaDiagnosis* Increased BT* Normal aPTT, PT in types 1 and 2 (A, B, M)* Elevated aPTT in types (2N and 3)* Plasma level of active vWF, measured as Ristocetin (an antibiotic) cofactor activity is reducedTreatment* Type 1: DDAVP (desmopressin) IV/intranasally* For other types - vWF replacement