Clinical features: Beta-thalassaemia is an inherited disorder of the blood caused by reduced production of part of the haemoglobin molecule. Haemoglobin is the oxygen carrying protein found in red blood cells. It is made up of four subunits, two alpha and two beta subunits. Beta-thalassaemia is due to reduced or absent production of the haemoglobin beta subunits, which results in severe anaemia. Individuals with beta-thalassaemia usually come to medical attention within the first two years of life. Without treatment affected children fail to thrive and have a shortened life expectancy. Repeated blood transfusions are required for normal growth and development and help to extend life. The condition is extremely variable and symptoms often correlate to the mutations in an affected individual.
Incidence: Common in people from the Mediterranean, the Middle East, South-East Asia and the Indian sub-continent. The highest incidences are reported in Cyprus (carrier frequency 1 in 7) and Sardinia (carrier frequency 1 in 8). The carrier frequency in Indo-Pakistanis is 1 in 15.
Inheritance: Autosomal recessive.
Gene: Beta-globin gene (HBB) on chromosome 11. More than 200 disease causing mutations have been identified to date. Despite this, four to ten mutations account for the majority of mutations in each at risk population.
Prenatal diagnosis: Yes. Please refer to your local clinical genetics service prior to a pregnancy. This ensures family members are offered appropriate advice and investigations, to confirm whether or not prenatal diagnosis is possible.
Carrier testing: Carriers of beta thalassaemia may be identified on a full blood count and show a microcytosis, hypochromia and a reduced MCV and MCH. There is also usually an elevated concentration of HbA2 (>3.5%), with or without an elevated concentration of HbF (>1.5%), as determined by haemoglobin electrophoresis.
UK Support Group: Thalassaemia Society UK 19 The Broadway Southgate Circus London N14 6PH Tel: 020 8882 0011 Fax: 020 8882 8618 Web: www.ukts.org
If you would like to access specialist information on beta-thalassaemia please go to:- Genetests - Beta-thalassaemia
Back to genetic conditions index
