Patients with hemophilia A has bleeding disorder because of-

Haemophilia is caused by quantitative reduction of factor VIII in 90% of cases well 10% cases have normal or increased level of factor VIII with reduced activity. factor VIII activates factor X the blood coagulation pathway. But in haemophilia A due to reduced activity of factor VIII ,It can not activate factor X.Therefore , no coagulation exists and increases bleeding. Reference: textbook of Pathology ,7th edition ,author Harsha Mohan, page number 313