A condition characterised by severe ANAEMIA, due to an abnormal form of HAEMOGLOBIN in the blood. It is an inherited disease which is widely spread across the Mediterranean through the Middle East and into the Far East. It has a particularly high incidence in Greece and in Italy. The abnormal haemoglobin prevents the affected red cells from functioning properly. This results in anaemia. The SPLEEN enlarges and abnormalities occur in the BONE MARROW. If someone inherits the disease from both parents, he or she is seriously affected but, if only one parent had the abnormal gene (see GENES), the person could well be free of symptoms. The severe form of the disorder is called thalassaemia major and affected individuals need repeated blood transfusions, possibly as frequently as every 6 weeks, as well as a CHELATING AGENT to remove excessive iron from their body resulting from the transfusions. The disease can be diagnosed by prenatal investigation.