Hemophilia

Hemophilia
An 8-month infant is brought into the office due to a swollen right knee and excessive bruising. The parents have noticed bruising about a month ago but thought the bruising was due to the attempts to crawl. They became concerned when the baby woke up with a swollen knee.

The infant up to date on all immunizations has not had any medical problems since birth and has met all developmental milestones.

• FH: negative for any history of bleeding disorders or other major genetic diseases.
• PE: within normal limits except for obvious bruising on the extremities and right knee. Knee is swollen but no warmth is appreciated. Range of motion of knee limited due to the swelling.
• DIAGNOSIS: hemophilia

Question:
What is the pathophysiology of Hemophilia