The Frequency of HBB Mutations Among ß-Thalassemia Patients in Hamadan Province, Iran.

ß-Thalassemia (ß-thal) caused by mutations on the HBB gene is the most common single-gene disorder in the world. In this study, the HBB gene mutation was investigated in Hamadan province, Iran. Forty-one patients referred to a referral hospital were admitted to the study. DNA samples were extracted from peripheral blood. The HBB gene was sequenced in all recruited patients. Eleven mutations and eight polymorphisms were found in the studied patients. IVS-II-1 (G>A) (HBB: c.315+1 G>A) was the most common mutation, accounting for 25.61% of mutant alleles. Other mutations included codon 8 (-AA) (HBB: c.25-26delAA); IVS-I-110 (G>A) (HBB: c.93-21 G>A); codons 8/9 (+G) (HBB: c.27-28insG); IVS-I-1 (G>A) (HBB: c.92 G>A); codon 44 (-C) (HBB: c.135delC); codons 25/26 (+T) (HBB: c.78-79insT); IVS-I-130 (G>C) (HBB: c.93-1 G>C); -28 (A>C) (HBB: c.-78 A>C); codons 36/37 (-T) (HBB: c.112delT) and IVS-I-6 (T>C) (HBB: c.92+6 T>C). According to our findings, the IVS-II-1 mutation has the highest prevalence in Hamadan Province. It was found that the total frequency of the IVS-II-1, codons 25/26 (+T), codons 8/9 (+G), IVS-I-110 and IVS-I-1 mutations was 82.92%. Therefore, given these findings, it is recommended that these five mutations are screened for as a first step in laboratories without sequencing instruments, and that the rest of the gene is subsequently examined.

Sensory neural hearing loss in beta-thalassemia major patients treated with deferoxamine.

This study evaluated the incidence of sensory neural hearing loss (SNHL) in beta-thalassemia major patients treated with deferoxamine in Mofid Children's Hospital. Based on the patients' file review, this descriptive and cross-sectional study was performed in all thalassemia patients older than 5 years old who were treated with regular blood transfusion and deferoxamine pump injection during the year 2006. The first visit with the otolaryngologist was performed in all patients to demarcate the presence of cerumen, otitis, and congenital abnormalities of ears. Then pure tone audiometery in frequency ranges of 250-8000 Hz was performed. Data statistical analysis was done by Mann-Whitney, chi square, and Fisher tests. There were 67 patients over 5 years old in our study. Five patients (7.4%), including 2 boys and 3 girls, in the age range of 7-24 years (mean:17.8 +/- 6.6 years) had SNHL. Their hearing loss was bilateral and in the frequency range of 2000-4000 Hz, with a mean of 3200 +/- 836.66 Hz. There were no significant differences between SNHL and non-SNHL patients in age, sex, serum ferritin level, age of the first transfusion, starting age of deferoxamine infusion, or duration and dosage of deferoxamine therapy. It seems that SNHL is not directly related to the serum ferritin level or deferoxamine dosage and other factors, including genetic or constitutional characteristics, may be also related. On the other hand, this complication may occur with doses lower than 50 mg/kg/day of deferoxamine, so no dosage can be considered safe for this drug. Despite the results of this study, hearing evaluation of beta-thalassemia major patients by audiometry is recommended because of the importance of this complication and the consequent disabilities.