Deficiency of clotting factor VIII or IX in the blood causes _________.

Haemophilia is a genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding. This results in people bleeding for a longer time after an injury, easy bruising, and an increased risk of bleeding inside joints or the brain.

Haemophilia A is the most common type and is caused by a deficiency of clotting factor VIII.

Haemophilia B is caused by a deficiency of clotting factor IX.

Therefore, the deficiency of clotting factor VIII or IX in the blood causes haemophilia.

Answer: haemophilia