None to severe/fatal. Alpha thalassemia signs and symptoms: silent carriers have no signs/symptoms (and live a normal life); Alpha trait has mild anemia (and generally live a normal life); HGB h (moderate) may have weakness, pallor, less growth, and need some transfusions; bart's disease (severe) is usually fatal before birth.
Incomp.with life. Alpha thalassemia is due to impaired production of Alpha globin chains, which leads to a relative excess of gamma globin chains in the fetus and newborn, and beta globin chains in children and adults. Since all normal hemoglobins of postnatal life contain Alpha chains, homozygous Alpha (0) thalassemia, in which no Alpha globin chains can be produced, is incompatible with life.