This is picked up on routine bloods such as partial thromboplastin times. The prothrombin time is usually normal. There is no excess bleeding after trauma. They may however still bleed excessively after surgery. In terms of treatment or therapy the factor XI level must be kept at greater than 30 % with fresh frozen plasma 5-20 ml./kg./ day. The inheritance is autosomal recessive.In Israel the incidence is 8% amongst Ashkenazi Jews. FactorXI deficiency is also known as; Rosenthal Syndrome or Haemophilia C. Sometimes the child may bleed excessively e.g. at circumcision but they do not bleed as severely as haemophiliacs (factor VIII deficiency) and rarely present with haemarthroses. Haemorrhage is usually from mucousal surfaces.