Why is it that alpha and beta -thalassemias result in more clinically severe diseases than other types of thalassemia?

Used for blood cells: Alpha globulin (made by the Alpha genes) and beta globulin (made by the beta genes) are the 2 globulin molecules needed to make normal adult hemoglobin (the red stuff in normal red blood cells). Mutations that prevent Alpha and beta globulin production will cause severe symptoms, but other mutations may not be as noticeable if the proteins the other genes make are not as crucial to life.

Anemia: These causes severe anemia with hemodynamic instability . The reason for these are genetic abnormality of the hemoglobin.