Complex interaction of hemoglobin (Hb) Nakhon Ratchasima [α63(E12)Ala→Val], a novel α2-globin chain variant with Hb E [β26(B8)Glu→Lys] and a deletional α(+)-thalassemia.

Objectives: To describe the hematological and molecular features as well as diagnostic aspects of a complex hemoglobinopathy caused by interaction of a novel α2-globin chain variant with hemoglobin (Hb) E and α(+)-thalassemia.

Methods: Blood specimen of a 41-yr-old Thai man was transferred to our center for the analysis of unknown Hb variant. Hb analysis was carried out using automated high-performance liquid chromatography (HPLC) and capillary electrophoresis system. Mutation was identified by PCR and related techniques.

Results: RBC analysis revealed a mild anemia but blood indices were within normal ranges. Hb-HPLC analysis demonstrated, in addition to the Hb E and Hb A, two abnormal peaks not fully separated from Hb A and Hb E, but capillary electrophoresis showed a pattern of Hb E heterozygote with 4.0% Hb A(2). DNA analysis of the α2 globin gene identified a novel mutation (namely Hb Nakhon Ratchasima), GCC (Ala)→GTC (Val) at codon 63 in trans to the α(+)-thalassemia (3.7-kb deletion). Association of this novel α-chain variant with β(E) globin chain leads to the formation of another novel Hb derivative with different HPLC characteristics.

Conclusion: Although Hb Nakhon Ratchasima might be clinically innocuous, differential diagnosis from other clinically relevant hemoglobinopathies is essential in routine setting. This could be made by using a simple PCR-restriction fragment length polymorphism assay or allele-specific PCR assay developed in this study.