Those with beta 0 produce no beta globin and thus have no Hb A Clinically, manifestations depend on the amount of Hb A. Thus, Hb-S-beta 0 thalassemia manifests similarly to sickle cell disease (Hb SS), whereas Hb S-beta+ thalassemia causes symptoms of moderate anemia and some signs of sickle cell disease, which are usually less frequent and less severe than those of pure sickle cell disease.