Disorders of Haemostasis Flashcards
(63 cards)
What causes disorders of haemostasis?
Deficiencies of coagulation factors that cause excessive bleeding
What are the two subcatergories of bleeding disorders?
Hereditary and aquired
What causes coagulation factor disorders?
Low levels of coagulation factors of disfunctional coagulation factors
What are general symptoms of bleeding disorders?
bleeding gums, bruises, purpura (blood spots) petichae, menorrhagia, joint bleeds, muscle bleeds, anaemia
What are the 4 main hereditary blood disorders:
Haemophilia A, Haemophilia B, Haemophilia C and Von Willebrand Factor Disease
What is Haemophilia A
Deficiency of FVIII (which is a cofactor for thrombin amplification)
It is either absent or in low levels.
The severity of the disorder depends on the severity of VIII deficiency.
NR: 50-150 IU/DL. 50% of cases have <1.0 IU/DL
What is the genetics behind Haemophilia A
X linked
What is the prevelance of haemophilia A?
Mostly in males, 1:10,000 males. 30% is spontaneous as no family history
What causes Haemophilia A?
Most common= inversion mutation of FVIII gene on intron 22. This results in total elimination of protien production with carying clinical severity
What are the symptoms of haemophilia A?
Begins in infancy: excessive bleeding after circumcision, excessive bruising once child becomes active
Muscle haematomas: abnormal collection of blood outside of blood vessel of muscle
Haemathroses: bleeding into joint spaces which damages the muscle as the blood pools in
Bleeds into the internal organs
Post-op and post-trauma haemorrhaging can be life threatening
What is haemophilia B?
Absence or low levels of IX.
Why is haemopholia B the same symtoms and prevelance?
Because IX and VIII are directly linked > VIII is cofactor for IXa.
How would you distinguish between haemophilia A and haemophilia B?
FIX assay - measuring the FIX levels
What is haemophilia C?
Deficiency of XI. It has variabe clinical severity and bleeding does not correlate with levels of XI. 8% of ashkenazi jews have FXI deficiency
Where is haemophilia treated?
specialised haemophilia centres
What is the treatment of haemophilia?
Prophalactic factor infusion theraphy (Factor infused directly into blood stream. Must be done 3x per week and can be done from home. Generally its recombinent genetically engineered factors. Increases levels from <1IU/L to >1IU/L
What does treatment of haemophilia achieve?
Stops crippling haemathroses. Although specialise care when post srugery and spontaneous bleeds, life expectancy is almost normal although contact sport not recommended without porphalxis.
How is haemophilia diagnosed in the labs?
Activated partial thromboplastin time test (APTT) which measures the intrinsic coagulation pathway. An extended of time indicates XII XI IX and VIII deficiency. Prothrombin time (PT) measures the extrinsic coagulation pathway. Abnormal times indicate VII synthesis so in haemophilia patients, PT should be normal Assay used to measure levels of coagulation factor - coagulation factor will be reduced Platelet function should be normal and bleeding time should be normal
What is the most common hereditary bleeding disorder
von willebrands disease - 1% of the population
What does vW disease cause?
Usually very mild symptoms, severity dependant on subtype. ‘pseudo’ haemophilia due to no haemathroses.
What causes vW disease?
qualative and quantiative defects of vWF either through abnormal levels of functioning vWF or normal levels of abnormal vWF.
What kind of inheritance is vWD?
autosomal dominant . Men and women affected but mostly women
What are the three subtypes of von willebrand disease?
Type 1- mild reduction of vWF
Type 2- functionally abnormal vWF
Type 3- total absence of vWF
What are the symtoms of vWD?
Mild to moderate bleeding disoders. More nosebleeds (epitaxis) and easy bruising. Excessive minor wound bleeds and heavy menstruation. Rarely life threatening. Haemathroses and muscle haematomas is rare except in type 3
