COINHERITANCE OF Hb S [β6(A3)Glu→Val, GAG>GTG] WITH β0-THALASSEMIA CODON 17 (A>T) IN A THAI PATIENT

Hb S [b6(A3)Glu -> Val, GAG>GTG] is a beta-globin gene variant that has a very low incidence in the Thai population. Coinheritance of Hb S and beta(0)-thalassemia (beta-thal) can result in severe clinical conditions. This study reports the case of a Thai patient with a compound heterozygosity for Hb S and beta(0)-thal codon 17 (A>T). His hemoglobin (Hb), hematocrit (packed cell volume, PCV), mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) levels were all less than the lower limits, while red cell distribution width (RDW) was higher than the upper limit. Levels of Hbs S, F and A(2) detected by high performance liquid chromatography (HPLC) were comparable to those from capillary electrophoresis (CE). As Hb S has a similar electrophoretic mobility and the HPLC profile is also similar to those of Hb Tak [beta 147, Term -> Thr (+AC)] and Hb D-Punjab [beta 121(GH4) Glu -> Gln, GAA>CAA], DNA equencing was then performed. This was to detect beta(0)-thal, and to differentiate Hb S from the Hb Tak and Hb D-Punjab mutations. The beta(0)-thal codon 17 and Hb S mutations were detected indicating that coinheritance of these two mutations can be found in the Thai population. Therefore, to provide proper clinical management and genetic counseling of this rare case, DNA analysis should be performed in all cases when a peak at the S-window is detected by HPLC or CE.