Hemophilia is a rare disorder in which your blood doesn't clot normally because it lacks sufficient blood-clotting proteins. The average age of people diagnosed with hemophilia is nine months. A blood test is used to detect whether you have it or not. It is located on the X-chromosome of a cell and is caused by a sex-linked recessive allele. Symptoms of hemophilia include sudden pain, repeated vomiting, extreme fatigue, double vision, and neck pain.