Phenotypic Variability in a Chinese Family with Nondeletional Hb H-Hb Quong Sze Disease

The Clinical Phenotypes of Alpha Thalassemia

Clinical manifestations of α-thalassemia range from no symptoms to severe transfusion-dependent anemia. Alpha thalassemia trait is deletion of 1 to 2 α-globin genes, whereas α-thalassemia major (ATM; Barts hydrops fetalis) is the deletion all 4 α genes. All other genotypes of intermediate severity are categorized as HbH disease, a vastly heterogenous group. Clinical spectrum is classified as mild, moderate, and severe by symptoms and need for intervention. Anemia in prenatal period may be fatal without intrauterine transfusions. New therapies to modify HbH disease or provide cure for ATM are under development.

Genetic counseling and prenatal decision for hemoglobin H disease caused by the rare α2 codon 30 (-GAG) (HBA2: c.91_93delGAG) mutation and the SEA deletion: Case series study

OBJECTIVE

We report a rare mutation on the α2-globin gene, HBA2: c.91_93delGAG and its potential functions.

CASE REPORT

We mainly described four patients with hemoglobin (Hb) H disease caused by the rare mutation and the SEA deletion but diversity in clinical presentation. Two had survived to adulthood with normal physical and mental development, except for mild anemia. However, two were children, who had more severe clinical manifestations. One child had developmental disorders of speech and language and mild growth retardation, and the other child suffered from severe hemolytic crises precipitated by infection and received blood transfusion.

CONCLUSION

This study is of great significance for clinicians to provide genetic counseling to couples at-risk of having offspring with Hb H disease and let them make the pregnancy decision, particularly reduce the occurrence of severe Hb H disease.

First Report of Nondeletional Hb H Disease Caused by an α2-Globin Gene Mutation: HBA2: c.184A>T

We report a rare mutation, HBA2: c.184A>T on the α2-globin gene, detected in a Chinese proband who presented with Hb H disease and a mild anemia. This frameshift mutation results in a premature termination of translation at position 61 of the α2-globin gene. Carriers of this mutation showed a borderline microcytic hypochromia. Our study indicates the importance of screening nondeletional α-thalassemia (α-thal) in areas with a particularly high prevalence of thalassemia such as in Southern China, especially for couples with one partner carrying an α⁰-thal deletion.

First Report of a Case with Nondeletional Hb H Disease Caused by IVS-I-116 (A>G) of the α2-Globin Gene

In this report, we describe a prenatal case with cardiomegaly and increased middle cerebral artery-peak systolic velocity (MCA-PSV) at 22 weeks' gestation. Fetal blood sampling revealed moderate anemia (Hb 7.4 g/dL) and increased Hb Bart's (γ4) level (28.2%), indicative of Hb H (β4) disease. Molecular analysis of the family members revealed that the pregnant woman carried a heterozygous IVS-I-116 (A>G) (HBA2: c.96-2A>G) mutation of α2-globin gene, and the fetus was a compound heterozygote for IVS-I-116 and the Southeast Asian (- -^SEA) deletion. This is the first reported case of nondeletional Hb H disease caused by the IVS-I-116 (A>G) mutation associated with fetal anemia identified by ultrasound.

Clinical Classification, Screening and Diagnosis for Thalassemia

At present, thalassemia diseases are classified into transfusion-dependent thalassemia and non-transfusion-dependent thalassemia. This classification is based on the clinical severity of patients determining whether they do require regular blood transfusions to survive (transfusion-dependent thalassemia) or not (non-transfusion-dependent thalassemia). In addition to the previous terminology of "thalassemia major" or "thalassemia intermedia," this classification has embraced all other forms of thalassemia syndromes such as α-thalassemia, hemoglobin E/β-thalassemia and combined α- and β-thalassemias. Definitive diagnosis of thalassemia and hemoglobinopathies requires a comprehensive workup from complete blood count, hemoglobin analysis, and molecular studies to identify mutations of globin genes.