Hb H disease among Tunisians: molecular characterization of alpha-thalassemia determinants and hematological findings

α-Globin Genotypes Associated with Hb H Disease: A Report from Oman and a Review of the Literature from the Eastern Mediterranean Region

α-Thalassemia (α-thal) is the most common autosomal recessive hemoglobinopathy. There is a vast diversity and geographical variability in underlying genotypes in Hb H (β4) patients. Herein, we describe the genotypes found in the largest report of Omani Hb H patients. Moreover, we reviewed and summarized the literature published from the Eastern Mediterranean region. A retrospective review of all genetically confirmed Hb H disease patients diagnosed between 2007 and 2017 at Sultan Qaboos University Hospital, Muscat, Oman, was performed. Hematological parameters and clinical presentations were assessed. Both α-globin genes were screened for deletional and nondeletional mutations using a stepwise diagnostic strategy as described before. A total of 52 patients (27 females and 25 males) with a mean age of 20.6 years (range 0.23-80.0) were molecularly confirmed to carry Hb H disease. The patients had a hemoglobin (Hb) level of 9.3 g/dL (range 5.7-13.0) and mean corpuscular volume (MCV) of 58.4 fL (range 48.2-82.1). A total of eight genotype combinations were identified, with α2 polyadenylation signal mutation (polyA1) (AATAAA>AATAAG (α^PA1α/α^PA1α), often cited as α^T-Saudiα/α^T-Saudiα, being the most common (53.8%) followed by -α^3.7/- -^{MED I} (28.8%). Our cohort also included patients with combinations of α^PA1 with other Hb variants: α^PA1α/α^PA1α with Hb S (HBB: c.20A>T) trait (n = 2), -α^3.7/α^PA1α (n = 2) and α^{codon 19}α (HBA2: c.56delG)/α^PA1α (n = 1). Nondeletional Hb H disease due to the α^PA1 mutation is the most common in Omanis. Molecular diagnosis is necessary for accurate confirmation of the diagnosis of α-thal, determination of underlying genotypes, follow-up and counseling.

α-Thalassemia frequency and mutations in children with hypochromic microcytic anemias and relation with β-thalassemia, iron deficiency anemia

The majority of the anemias during childhood are hypochromic and microcytic. The aim of the present study was to determine the status of α-thalassemia mutations and its association with other etiologies, such as iron deficiency anemia (IDA) and β-thalassemia trait, that are frequently seen hypochromic microcytic anemias in children. Children with hypochromic microcytic anemias were included in the study. Serum iron (SI), total iron-binding capacity (TIBC), ferritin levels, and hemoglobin electrophoresis with high-performance liquid chromatography (HPLC) method were analyzed. Reverse hybridization of biotinylated polymerase chain reaction (PCR) product method was used for detection of α-globin gene mutations. Of the 46 patients involved in the study, 54.3% (n = 25) were boys, and 45.7% (n = 21) were girls. Iron deficiency anemia and β-thalassemia trait were diagnosed in 67.4% (n = 31) and 19.5% (n = 9), respectively. In 17.4% there were α-thalassemia mutations (in 10.9% 3.7 single-gene heterozygote mutation, in 4.3% 20.5-kb double-gene deletion mutation, and in 2.2% α-2 poly-A-1 heterozygote mutation was detected). In 2 patients (4.3%) no etiology was determined. In 2 patients (4.3%) association between iron deficiency anemia and α-thalassemia, in 1 patient (2.2%) association between β and α-thalassemia was detected. In conclusion, α-thalassemia carrier status and its association with other etiologies are frequently seen in Manisa. So, α-thalassemia should be considered in the differential diagnosis of hypochromic microcytic anemias, especially in cases without iron deficiency (ID) and β-thalassemia carrier state.

Hb A2-Pasteur-Tunis [δ59(E3)Lys→Asn, AAG→AAC]: A New δ Chain Variant Detected by DNA Sequencing in a Tunisian Carrier of the Codon 39 (C→T) β0-Thalassemia Mutation

We describe a new delta-globin variant, Hb A2-Pasteur-Tunis [delta59(E3)Lys-->Asn, AAG-->AAC]. This hemoglobin (Hb) displayed an electrophoretic mobility faster than normal Hb A2 and was expressed at 2.2 %. The molecular defect was characterized by DNA sequencing and confirmed by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-designed protocol. Hb A2-Pasteur-Tunis was found in a carrier of a codon 39 (C-->T) beta0-thalassemia (thal), presenting with a normal Hb A2 level. Phenotype and genotype investigations revealed that the total Hb A2 level of the patient was that expected for a minor beta-thal (4.8%).