Pseudotumour of bone in a haemophiliac with circulating antibodies to factor VIII. Recovery after rupture of cyst wall without necrosis or perforation of the skin.

A 15-year-old boy with severe haemophilia A and circulating antibodies to factor VIII, developed a pseudotumour with osteolysis of the tibia. He made a complete recovery following what seemed to be a spontaneous inward rupture of the cyst wall.