Thalassemia is a group of inherited blood disorders affecting hemoglobin, the oxygen-carrying protein complex of the red blood cell. Hemoglobin is made up of alpha and beta globin chains and those with thalassemia have an absence or mutation of the genes encoding these proteins. The specific mutation a person inherits will determine the type and severity of their thalassemia. The two types of thalassemia are alpha thalassemia and beta thalassemia and both can range in severity from mild to severe.
Thalassemia has been encountered in virtually every ethnic group and geographic location and is the most common genetic disorder in the world, affecting nearly 200 million people worldwide. It is most common in the Mediterranean and regions of Asia and Africa. Alpha thalassemia occurs most often in persons of African and Southeast Asian descent, and beta thalassemia is most common in persons of Mediterranean, African, and Southeast Asian descent. The thalassemia trait affects 5 to 30 percent of persons in these ethnic groups.
Historically, like sickle cell anemia, thalassemia is seen to be most common in areas that are endemic with malaria. Thalassemia heterozygotes appear to have a possible survival advantage with regards to malaria, in which the malarial parasite results in a milder disease.
People with thalassemia, due to a defect or absence of hemoglobin production, may experience a lack of oxygen in the bloodstream which can cause signs and symptoms such as fatigue, slowed growth and delayed puberty, bone problems such as osteopenia and osteoporosis, mild to severe anemia, or enlarged spleen, liver, or heart. Symptoms will depend on the type and severity of the thalassemia a person has.
Those who inherit one normal hemoglobin gene from one parent and a defective gene from another parent are considered to be silent carriers and will not have any symptoms.
It is important to identify patients with thalassemia trait for two reasons:
Diagnosis can be done through blood tests such as a complete blood count, which may reveal a mild, microcytic anemia. Further testing typically includes serum ferritin and hemoglobin electrophoresis. In the Greater Vancouver area, hemoglobin electrophoresis results include the laboratory physician's interpretation and any recommendations for further workup, such as molecular testing.
Prenatal genetic testing, using procedures such as amniocentesis and chorionic villi sampling, is also available and can be done as early as 10-11 weeks in pregnancy.
Treatment depends on the type and severity of the thalassemia and can range from no treatment in an asymptomatic individual to regular blood transfusions and chelation therapy.
Muncie HL and Campbell JS. Alpha and Beta Thalassemia. Am Fam Physician 2009; 80(4):339-344
WHO - Thalassemia
Hoffman R, Furie B, McGlave P et al. Hematology. 5th Edition. Orlando: W. B. Saunders; 2009. 2560 p.
CDC - Thalassemia
Thalassemia International Federation
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