Thalassemias are inherited blood disorders characterized by decreased hemoglobin production. Symptoms depend on the type and can vary from none to severe. Often there is mild to severe anemia (low red blood cells or hemoglobin). Anemia can result in feeling tired and pale skin. There may also be bone problems, an enlarged spleen, yellowish skin, and dark urine. Slow growth may occur in children.

Thalassemias are genetic disorders. There are two main types, alpha thalassemia and beta thalassemia. The severity of alpha and beta thalassemia depends on how many of the four genes for alpha globin or two genes for beta globin are missing. Diagnosis is typically by blood tests including a complete blood count, special hemoglobin tests, and genetic tests. Diagnosis may occur before birth through prenatal testing.

Treatment depends on the type and severity. Treatment for those with more severe disease often includes regular blood transfusions, iron chelation, and folic acid. Iron chelation may be done with deferoxamine, deferasirox or deferiprone. Occasionally, a bone marrow transplant may be an option. Complications may include iron overload from the transfusions with resulting heart or liver disease, infections, and osteoporosis. If the spleen becomes overly enlarged, surgical removal may be required. Thalassemia patients who do not respond well to blood transfusions can take hydroxyurea or thalidomide, and sometimes a combination of both. Hydroxyurea is the only FDA approved drug for thalassemia. Patients who took 10 mg/kg of hydroxyurea every day for a year had significantly higher hemoglobin levels, and it was a well-tolerated treatment for patients who did not respond well to blood transfusions. Another hemoglobin-inducer includes thalidomide, although it has not been tested in a clinical setting. The combination of thalidomide and hydroxyurea resulted in hemoglobin levels increasing significantly in transfusion-dependent and non-transfusion dependent patients

As of 2015, thalassemia occurs in about 280 million people, with about 439,000 having severe disease. It is most common among people of Greek, Italian, Middle Eastern, South Asian, and African descent. Males and females have similar rates of disease. It resulted in 16,800 deaths in 2015, down from 36,000 deaths in 1990. Those who have minor degrees of thalassemia, similar to those with sickle-cell trait, have some protection against malaria, explaining why they are more common in regions of the world where malaria exists.