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Hb E [β26(B8)Glu→Lys; HBB: c.79G > A]-β-thalassemia (β-thal) has an extremely variable clinical presentation. We report the clinical features of these patients from five Indian states together with their hematological and molecular characteristics. Seventy-eight Hb E-β-thal patients from different regions [West Bengal (30), Maharashtra (21), Uttar Pradesh (13), Bihar (11), Orissa (3)] were clinically evaluated along with hematological profiles and molecular characteristics (β-thal mutations, XmnI polymorphisms, α genotypes). Twenty-nine of the 78 patients had a mild clinical presentation (clinical score 2.2 ± 1.1), while 15 had moderate severity (clinical score 6.1 ± 1.2) with occasional transfusion needs, and 34 patients were severely affected (clinical score 8.2 ± 0.5) requiring regular blood transfusions. The age at clinical presentation in the severely affected patients was lower (6 months-10 years) as compared to those with milder symptoms (2 years-34 years). Thirty-four patients showed splenomegaly (spleen ≥3 cm below the costal margin) and five patients were splenectomized. The severe βIVS1-5 (G > C) (HBB: c.92 + 5G > C) was the most common β-thal mutation, while seven other mutations were also seen. The XmnI [+/+] and [-/-] polymorphisms were seen in 24.1 and 10.3% of mildly affected patients and 14.7 and 17.6% of severely affected patients respectively. A single α gene deletion (-α/αα) was found in 20.7% of mildly affected and 5.9% of severely affected patients, respectively. No specific differences in the clinical, hematological or molecular characteristics were observed in the Hb E-β-thal patients from various geographic regions or different ethnic groups.

No abstract

These results indicate that the (TA)7/(TA)7 configuration is one of the factors responsible for hyperbilirubinemia and, therefore, seems to interfere with the clinical expression of homozygous beta thalassemia. This emphasizes the role played by co-inherited modifying genes on clinical heterogeneity of monogenic disorders.