Background and objective: Hemoglobin S (HbS) alpha-thalassemia together with ss-thalassemia and hemoglobins C, E and D are named common hemoglobinopathies. In this study, we analyzed the frequency of the association between alpha-thalassemia and HbS and its phenotypic expression.
Patients and method: Since January 1995 to March 2003 we studied 83 cases of HbS, which were diagnosed by electrophoretic and chromatographic criteria. The molecular study was carried out by Southern blot with the restriction enzymes Bam HI and Bgl II and a (1.5 Kb Pst) and z (1.8 Kb Sac Y) probes.
Results: 45 cases (54.2%) had a-thalassemia (36 -alpha3,7/aa; 1-alpha4,2/alphaalpha; 6 -alpha3,7/-alpha3,7; 1-alpha4,2/-alpha4,2); 36 had not alpha-thalassemia and in two cases there were a triplication of a genes. The patients with HbS heterozygote associated with alpha-thalassemia showed a percentage of HbS (p < 0.0001), CMV (p = 0.004), MCH (p = 0.002) and MCHC (p = 0.02) significantly lower than the cases of HbS without this association. However, no differences between both groups were found with regard to the rest of parameters analyzed (Hb p = 0.56; PVC p = 0.84; RDW p = 0.06; Reticulocytes p = 0.26; HbF p = 0.76; HbA2 p = 0.13). In the cases with a severe form of disease (HbS homozygote; HbS/Hb C; HbS/beta-thalassemia), patients with alpha-thalassemia had a number of leukocytes that was significantly lower than that of patients without alpha-thalassemia (p = 0.034).
Conclusion: An association between HbS and alpha-thalassemia was common (> 50%). Screening for this association is of great interest because the clinical expression in the cases of HbS homozigote will be modulated. This association must be suspected in cases of homozygous HbS in which levels of HbS are lower than expected.