Haemophilia is a hereditary disease manifested by increased bleeding. Even slight bruises can cause extensive haemorrhages, both subcutaneous and intramuscular. Repeated haemorrhages in the joints result in serious changes in them, which are characteristic of haemophilia. Normally non-severe injuries (cuts, for example) and surgery (tooth extraction) are accompanied by life-threatening bleeding. Haemophiliacs must stringently curtail their activities, which means that they, especially when young, may be isolated from their peer groups. Many haemophiliacs were infected with AIDS through the blood transfusions upon which they depend before 1985, when new methods of screening rendered the treatment safe from this infection.