Justin a 5 year old boy was referred to a dentist by a pediatrician. The dentist was about to administer an anesthetic drug by injection prior to extracting tooth when he elicited a history of easy bruising in the boy. Justin has had several instances of severe bruising following minor trauma. The family history also revealed of his brother who died at age one from an intracranial hemorrhage after falling from a crib. 

The routine hematological investigations revealed there is a severe deficiency of clotting factor number VIII. 

Justin is diagnosed with __________.