Summary

• There are at least 4 different and distinct alpha-thalassaemias: silent carrier (1 affected alpha-globin gene), alpha-thalassaemia trait (2 affected alpha-globin genes), Hb H disease (typically 3 affected alpha-globin genes), and Hb Bart hydrops fetalis syndrome (typically deletion of all 4 alpha-globin genes).
• The severity of the clinical manifestations of anaemia and haemolysis correspond with the genetic defect and the degree of impairment in alpha-globin synthesis.
• Alpha-thalassaemia is found in malarial regions of the world (Mediterranean, South-east Asia, Indian sub-continent, Middle East, Sub-Saharan Africa) and should be suspected in patients with these ethnic backgrounds and with microcytosis and/or anaemia.
• The vast majority of alpha-thalassaemia patients are clinically well and most are asymptomatic. Many patients with Hb H are also clinically well, but are at risk for: acute haemolytic episodes; aplastic crises; iron overload, even in the absence of chronic transfusions; hypersplenism; and endocrine disease.
• Education is an important part of management and should cover both the risks of acute events and, in genetic counselling, the risks of conceiving a child with Hb H disease or the potentially devastating Hb Bart hydrops fetalis.
• Acquired Hb H disease is rare and occurs in association with haematological disorders, most commonly in male patients with myelodysplastic syndrome.