All forms of thalassemia are inherited.
The disease is passed on through parents who carry the thalassemia gene in their cells. A “carrier” has one normal gene and one thalassemia gene, a state sometimes called “thalassemia trait”. Most carriers lead completely normal, healthy lives.
When two carries become parents, for every pregnancy there is a one-in-four (25%) chance that the child will be affected by Thalassemia Major; there is a two-in-four (50%) chance that the child will become a carrier and one-in-four (25%) chance that the child will be completely unaffected.
In Italy the number of carrier is roughly estimated as three millions.