Thalassemia is inherited, meaning that at least one of your parents must be a carrier of the disease. It’s caused by either a genetic mutation or a deletion of certain key gene fragments. Thalassemia minor is a less serious form of the disorder. There are two main forms of thalassemia that are more serious. In alpha thalassemia, at least one of the alpha globin genes has a mutation or abnormality. In beta thalassemia, the beta globin genes are affected. Each of these forms of thalassemia has different subtypes. The exact form you have will affect the severity of your symptoms and your outlook.