Chapter 24: Coagulation disorders Flashcards
What are the most common disorders involving coagulation factors?
(1) Hemophilia A (factor VIII)
(2) Hemophilia B (Factor IX)
(3) vWD
What is the epidemiology of Hemophilia A?
30-100 out of a million. The disorder is sex linked however up to one third of the cases are due to spontaneous mutations.
What is the cause of Hemophilia A?
Defective or deficient factor VIII.
What are the clinical features/presenting symptoms of hemophilia A?
Hemophilia A causes excessive bruising and bleeding along with hemarthroses and hematomas.
What are hemophilic pseudotumors?
Large encapsulated hematomas with progressive cystic swelling.
Why did a large proportion of hemophiliacs become HIV positive?
Before the blood testing hemophiliacs would contract HIV from the many blood transfusions they would receive. (HCV as well)
What are the abnormal lab values associated with hemophilia A?
(1) abnormal activated partial thromboplastin time
(2) Abnormal Factor VIII clotting assay.
(3) Bleeding time and prothrombin time are normal.
How is hemophilia A treated?
(1) Factor VIII replacement (for bleeding episodes)
2) Desmopressin (DDAVP) stimulates endothelial cells to release Factor VIII. can be used for milder hemophilias
What prophylactic measures can be undertaken in the treatment of Hemophilia A?
Factor VIII infusion three times a week and avoidance of rough physical contact can limit the occurance of bleeding episodes.
What levels of Factor VIII or IX are necessary to avoid most of the mortality and morbidity?
Factor VIII or IX levels above 1% are usually high enough to avoid morbidity.
What is one of the most serious complications of factor VIII therapy?
Some patients develop antibodies against factor VIII.
What differentiates factor VIII deficiency from factor IX deficiency?
The only difference is the specific clotting assay that used to identify it. Hemophilia B is less common.
What lab findings dare associated with Hemophilia B?
(1) Abnormal APTT
(2) Factor IX clotting assay.
What is the normal role of vWF?
vWF facilitates platelet adherence to the ECM and it binds factor VIII.
What is the most common inherited bleeding disorder?
von Willebrand Disease. Autosomal dominant
What lab findings are associated with vWD?
(1) prolonged bleeding time
(2) Low factor VIII levels
(3) prolonged APTT
(4) Low vWF
(5) Defective platelet aggregation with ristocetin.
(6) collagen binding function is usually reduced.
How is vWD treated?
(1) antifibrinolytic agents (tranexamic acid)
(2) desmopressin (DDAVP)( Type 1 vWD)
(3) vWF and factor VIII concentrates
From where is vitamin K absorbed?
Vegetables and bacterial synthesis in the gut.
what conditions can cause a vitamin K deficiency?
malabsorption, inadequate diet, and inhibition of vit K by drugs.
What clotting factors are dependent on vitamin K?
Factors II, VII, IX, X, C, And S.
What is the role of Vit K as a cofactor?
Vitamin K converts PIVKA into the proper clotting factors.
How does warfarin inhibit clotting?
Warfarin inhibits the reduction of vitamin K back into its active form after it has preformed its function. This leads to a functional vitamin K deficiency.
What is hemorrhagic disease of the newborn?
Newborns are usually deficient in vitamin K this leads to bleeding.
How is hemorrhagic disease of the newborn diagnosed?
Most findings are normal except for excessive bleeding and absent fibrin degradation products.
