Silent carrier
This form of thalassemia is caused when one of the four alpha genes is missing or damaged. Called "silent carriers," people with this illness have no symptoms, and can only be diagnosed by specialized DNA testing or a minor abnormality on newborn screening.
Alpha thalassemia trait
This condition is caused by defects on or the absence of two of the four alpha chains, either on the same chromosome ("cis" deletion) or one from each ("trans" deletion). People with this form of the illness may have mild anemia, but look and feel normal. This condition can be diagnosed through routine blood tests. If both parents have the "cis" deletion, there is a one-in-four chance with each pregnancy that the child will have the most serious form of the disease, alpha thalassemia major. DNA testing can determine which form of the illness the parent carries.
Hemoglobin H disease
The loss of three alpha genes causes a severe form of thalassemia known as hemoglobin H disease. People with this form of the illness have severe anemia and may require frequent blood transfusions to survive. Other complications, such as iron overload, which can lead to organ damage, may occur. Patients with this form of thalassemia require careful monitoring and expert medical management. People with hemoglobin H disease are also at increased risk of having children with the most serious form of the illness, alpha thalassemia major, so genetic counseling and screening is important in adulthood.
Alpha thalassemia major
The most serious form of thalassemia is caused by the loss of all four alpha genes. This form of the illness usually results in fetal or newborn death. If the condition is diagnosed early enough, in utero blood transfusions have been used to save the life of the child. People with this form of the illness require life-long transfusions and extensive medical services.
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