Beta-thalassemias associated with hemoglobin (Hb) anomalies result in a variable clinical spectrum, ranging from asymptomatic to severe, depending on the severity of the thalassemia mutation and on the type of the Hb anomaly [hereditary persistence of fetal Hb, delta-beta-thalassemia, Hb C - beta-thalassemia, Hb E - beta-thalassemia and Hb S - beta-thalassemia (see these terms)].