Haemophilia

Question 1

What is haemophilia?

Answer 1

A condition where the ability of the blood to clot is severely reduced due to insufficient thrombin generation, causing severe bleeding even from a minor injury

Question 2

What is haemophilia typically caused by?

Answer 2

Hereditary lack of coagulation factor, most often F8 or F9

Question 3

What are the two types of haemophilia?

Answer 3

A and B

Question 4

What is haemophilia A caused by?

Answer 4

Deficiency of F8

Question 5

What is haemophilia B caused by?

Answer 5

Deficiency of F9 (Christmas disease)

Question 6

What do haemophilia A and B have in common?

Answer 6

• Both X-linked recessive
• Females are carriers but mainly expressed in males
• Relatively rare

Question 7

How does a deficiency of F8 (A) affect coagulation pathway?

Answer 7

F8 is cofactor of F9 in the conversion of F10 to F10a (intrinsic pathway)

Question 8

How does a deficiency of F9 (B) affect coagulation pathway?

Answer 8

F9a converts F10 to F10a (intrinsic pathway)

Question 9

How are F8 and F9 involved in formation of thrombin?

Answer 9

F8 and F9 form a complex on the surface of the platelet. This complex is essential for F10 to form F10a. In the absence of F8 or F9, F10 isn’t activated and thrombin isn’t formed

Question 10

What does insufficient thrombin lead to?

Answer 10

Can’t cross-link fibrinogen to fibrin so the platelet plug is weak, leading to bleeding

Question 11

What are normal, mild, moderate and severe F8 or F9 levels?

Answer 11

Normal - 50-150%
Mild - 6-50%
Moderate - 1-5%
Severe - <1%