Thalassemia

Hemoglobin is the oxygen-carrying protein in red blood cells. It is built from globin components, including alpha and beta chains. In thalassemia, inherited variants reduce the production of one of these components, leaving the body with too little normally functioning hemoglobin. Red blood cells may develop or survive less well, producing anemia and reducing the delivery of oxygen to tissues. The term therefore covers several related conditions rather than one disease with a single genetic cause.

The two main categories are alpha thalassemia and beta thalassemia, named for the globin component whose production is reduced. Alpha thalassemia usually involves changes or deletions in the HBA1 or HBA2 genes. A person has four alpha-globin gene copies, and the combination affected influences the form and severity, from carrier states to HbH disease or the much more severe Hb Bart syndrome. Beta thalassemia involves variants in the HBB gene. These can prevent beta-globin production or reduce it; clinical forms include trait or minor, intermedia, and major. Inheritance is not identical across every form, and the specific variants matter.

The effects vary widely. Some people with a thalassemia trait have no symptoms, while others have mild anemia. More serious forms can cause fatigue, weakness, pale skin, or shortness of breath. Severe forms may become apparent in infancy or childhood and can affect growth; complications can involve bones and organs. These differences reflect the specific variants and their effects on hemoglobin production; a carrier or trait label does not imply the same clinical course as major disease.

Blood tests can identify anemia and help characterize hemoglobin, and genetic testing can clarify the inherited form. Carrier testing and screening are also used in some settings. Care depends on the type and severity: people with mild trait forms generally do not need transfusions, whereas some people with moderate or severe disease receive them. Repeated transfusions can cause excess iron to accumulate, so some patients also receive iron-chelation treatment. These approaches require clinical assessment and monitoring; the needs of one person cannot be inferred from the diagnosis alone.

Thalassemia occurs worldwide, but carrier variants are more common in populations with family origins in parts of the Mediterranean, Africa, the Middle East, South Asia, Southeast Asia, and Central Asia. These are patterns of increased frequency, not geographic boundaries: thalassemia can occur in people from any ancestry.