Clinical Laboratory Manifestation and Molecular Diagnosis of β-Thalassemia Patients in Iraq

Cord Blood Hematological Parameters of Fetuses Detected Different Thalassemia Genotypes in the Second Trimester of Pregnancy

Background

Hemoglobinopathies are the most common inherited diseases in humans resulting from impaired globin chain synthesis of hemoglobin. The progression of thalassemia rates is prevented with prenatal screening methods.

Aims

To evaluate the hematological parameters of α- and β-thalassemia and normal fetuses aged 17-25 weeks of gestation.

Study Design

A cross-sectional study.

Methods

Pregnant women who underwent cordocentesis in the second trimester because of the risk of having a baby with thalassemia were included in the study. Hematological indices and molecular DNA methods were analyzed from the cord blood samples of 129 women who were 17-25 weeks into pregnancy. The HPLC method was used for Hb fraction analysis. Amplification refractory mutation system, restriction enzyme analysis, multiplex polymerase chain reaction, and sequencing methods were used for the molecular analysis. Maternal contamination was eliminated by the short tandem repeat method.

Results

In total, 112 of the fetuses carry α- and β-thalassemia heterozygous or homozygous (α: 37, β: 58, mixed: 17) and 17 fetuses had a normal genotype for thalassemia. Significant differences in adult hemoglobin (HbA), fetal hemoglobin (HbF), Hb Barts, MCV, MCH, and RDW were detected in three groups compared with the normal group (p < 0.001, except for RBC, Hb, HCT, and MCHC). Differences in HbF, Hb Barts, MCV, MCH, and RDW were observed in the α-thalassemia groups compared with the normal group (p < 0.001). Among the five β-thalassemia subgroups, only HbA and RDW were different from the normal group (p < 0.001).

Conclusion

This study could be a good reference for future studies and prenatal diagnostic applications in emphasizing the importance of changes in the blood parameters of fetuses before molecular genotyping. These hematological data give valuable information to clinicians about the fetus to enlighten families in making appropriate decisions during prenatal diagnosis.

Identification of novel mutations in β-thalassemia patients in Maysan Governorate, Iraq

BACKGROUND

In homozygous β-thalassemia, the primary genetic modifiers affecting the clinical severity of β-thalassemia are genetic variants and the ability to reduce globin chain imbalance, thus resulting in a milder form of thalassemia. However, there are few reports on the molecular genetics of β-thalassemia in Iraq.

METHODS

We performed PCR and DNA sequencing on 40 Iraqi patients who were clinically suspected of having β-thalassemia.

RESULTS

The first genetic sequencing study was conducted in Maysan Governate, Iraq, using patients from various locations to identify novel mutations. There were five novel mutations: 294.T>C 12% (city center and Almajar district), 205. C>T 25% (city center, Alsalam, and Almashrah districts), 289.G>A 38% (Almaymuna and Gleat Salih districts), 49.T>C 32% (city center), and 624.C>A 32% (city center). These mutations were identified among β-thalassemia patients by two regions of HBB gene 696 bp and 861 bp.

CONCLUSIONS

The discovery of new genetic variants helps predict the severity of β-thalassemia disease. There are relatively few studies in molecular genetics of β-thalassemia in Iraq, and the new mutations reported here will provide valuable data for the prevention and control of β-thalassemia in Maysan Governate, Iraq. The results can lead to new genetic sequencing investigations for other Iraqi regions.

A First Clinical and Molecular Study of Rare IVS-II-806 (G > C) (HBB:c.316-45G > C) Variant in the β-globin Gene: A Possibly Benign Variant

Introduction

β-thalassemia is a common genetic disease affecting a single gene, disease with a high incidence in South China. We hereby, aim to provide the clinical and hematological features of a rare β-globin gene variant in the Chinese population.

Methods

Ten subjects from three unrelated Chinese families were enrolled in this study. Hematological analysis and thalassemia gene testing were preformed to screen for common α and β-thalassemia variants. Gap-polymerase chain reaction (Gap-PCR) and DNA sequencing were utilized to examine the rare or novel thalassemia variants.

Results

Six cases were identified carrying the rare IVS-II-806 (G > C) (HBB:c.316-45G > C) variant in the β-globin gene. The proband in family 1 carry three rare β-globin gene mutations including CD39 (C > T), IVS-II-81 (C > T) and IVS-II-806 (G > C) combined with a --SEA/αα deletion, exhibiting the β-thalassemia trait. Further pedigree investigation indicated that the genotype of the proband in family 1 was --SEA/αα, βCD39 (C>T), IVS-II-81(C>T)/βIVS-II-806(G>C). Meanwhile, the twin girls in family 1 carrying the IVS-II-806 (G > C) mutation demonstrated a normal hematological phenotype. In family 2, the proband and his sister carry the IVS-II-806 (G > C) mutation, eliciting high levels of Hb A2 and slightly low levels of MCV and MCH. Moreover, the proband in family 3 carrying the same mutation exhibited a slightly low MCV level as well.

Conclusions

In this study, clinical and hematological analysis of the IVS-II-806 (G > C) mutation was first conducted within the Chinese population, with results indicating that it may be a benign variant.

IVS-II-16 (G>C) (HBB: c.315+16G>C) or IVS-II-666 (C>T) (HBB: c.316-185C>T) Mutations Trigger an Hb S (HBB: c.20A>T)/β+-Thalassemia Phenotype in an Hb S Trait Patient

Sickle cell trait is a medical condition caused by the presence of both mutant Hb S (HBB: c.20A>T) and normal Hb A alleles. Although sickle cell trait is typically considered to be asymptomatic and benign, genetic modifiers and mutations can lead to severe clinical complications. In this study, the possible pathogenicity of the IVS-II-16 (G>C) (HBB: c.315+16G>C) and IVS-II-666 (C>T) (HBB: c.316-185C>T) mutations, which are considered to be neutral polymorphisms, and the association between the Hb S mutation are presented. To the best of our knowledge, these polymorphisms have not been previously reported in any sickle cell trait patient, and no relevant studies have been conducted. We recently studied a 40-year-old woman (proband), diagnosed to be an Hb S/β-thalassemia (β-thal) carrier. β-Globin mutations were analyzed using a DNA sequencer based on the Sanger method. The HbVar and ClinVar databases show IVS-II-16 and IVS-II-666 to be intronic mutations. However, statements in these data banks contradict our findings. In the present study, a transfusion-dependent Hb S patient, behaving as an Hb S/β-thal case due to these mutations, was reported. These mutations have not been previously reported in an Hb S patient. Although the IVS-II-16 and IVS-II-666 mutations were previously reported as benign, they converted the Hb S phenotype to transfusion-dependent Hb S/β-thal when combined with Hb S. In this regard, IVS-II-16 and IVS-II-666 mutations may not be innocent, as previously thought.