RESUMEN
beta-Globin mutations with Xmnl site might be associated with elevated HbF expression which may in turn ameliorate the severity of p-thalassemia phenotype. To investigate the frequency of -158 [C > T] Xmnl polymorphism among Egyptian Children and young adults with p-thalassemia, to examine the relationship between Xmnl polymorphism and p-thalassemia genotypes and phenotypes and to assess the possible relation of Xmnl polymorphism and response to hydroxyurea [Hu] therapy. Seventy-two P-thalassemia patients [37 females; M/F ratio 0.95] with a mean age of 7.53 +/- 6.99 were included. Laboratory investigations included Complete blood count [CBC], Hb electrophoresis by high performance liquid chromatography [HPLC], p-thalassemia mutation identification by the reverse dot blot hybridization technique [RDB] and detection of XmnlGg polymorphism by RFLP. The frequency of positive heterozygote Xmnl gene polymorphism was 8.3%. Eighty-three percent of XmnIGy [+] patients were never transfused [p = 0.001] and had higher total hemoglobin compared to XmnlGy [p = 0.01]; while mean HbF was higher among XmnIGy patients compared to the other group but the difference was marginally insignificant [p = 0.06]. p-Thalassemia mutation TVS II-1 showed relatively higher Xmnl polymorphism frequency [50%] and followed by its frequency among 10 undefined P-thalassemia mutations which was 20%. The frequency of positive heterozygote Xmnl gene polymorphism was 11.6% among the TI group vs. 3.5% among the TM group [p = 0.4]. Among 20 cases who received HU; 5/14 responders vs. I/ 6 none responder had positive heterozygote Xmnl gene polymorphism [p = 1.0]. In conclusion, molecular determination of genetic markers in childhood will help to identify phenotypes of our patients and to avoid over or under treatment strategies. Further prospective studies concerning the genetic markers that could predict the response to hemoglobin F inducers like hydroxyurea are highly recommended