Question

Deficiency of factor VIII (antihaemophilic globulin) 

A. Increases the bleeding time. 

B. Is due to an abnormal gene on the Y chromosome. 

C. To 75 per cent of its normal value results in excessive bleeding after tooth extraction. 

D. Causes small (petechial) haemorrhages into the skin to cause purpura. 

E. Affects the extrinsic, rather than the intrinsic, pathway for blood coagulation.

Answer 1

A. False Clotting time is increased, but bleeding time is determined by platelets and by vascular contraction. 

B. False It is due to a recessive abnormality of the X chromosome. 

C. False Abnormal bleeding does not occur until the level falls below 50 per cent. 

D. False Purpura is caused by capillary or platelet disorders. 

E. False It affects the intrinsic pathway.