Thalassaemia is the name for a group of inherited conditions that affect a substance in the blood called haemoglobin.
People with the condition produce either no or too little haemoglobin, which is used by red blood cells to carry oxygen around the body. This can make them very anaemic (tired, short of breath and pale).
It mainly affects people of Mediterranean, South Asian, Southeast Asian and Middle Eastern origin.
There are a number of types of thalassaemia, which can be divided into alpha and beta thalassaemias. Beta thalassaemia major is the most severe type. Other types include beta thalassaemia intermedia, alpha thalassaemia major and haemoglobin H disease.
It's also possible to be a "carrier" of thalassaemia, also known as having the thalassaemia trait. Thalassaemia carriers don't have any serious health problems themselves, but are at risk of having children with the condition.