GSTM1 and sickle cell-beta-thalassemia disease syndrome: Based on Hb electrophoresis analysis before the initiation of hydroxyurea (HU) treatment 59 (58%) patients had HbSS with high HbF, 23 (22.8%) had HbSS disease, 18 (17.8%) had sickle beta thalassemia, and 1 (1%) had HbSC disease.