Hb H (β₄) Disease in Çukurova, Southern Turkey

Abstract

In this study, 32 patients with Hb H (β₄) disease have been identified. Three different α-thalassemia-1 (thal) determinants; nine with the −17.4 kb (MED I) type, 12 with the −20.5 kb type and 10 with the −26.5 kb (MED II) type were characterized. Of the 32 patients, 19 had the 3.7 kb deletion and one had the 4.2 kb deletion in trans to α-thal-1 determinants. Only one patient, homozygous for the polyadenylation signal (poly A) site (PA 1) mutation, was identified to be associated with Hb H disease. The other patient had the poly A (PA 1) mutation in trans to the MED I (−17.4 kb) determinant. The 5 nt (nucleotide) deletion was present in three patients, two of them in the same family; this mutation was found in association with the MED II (26.5 kb deletion). The other patient had the −5 nt mutation in trans to the MED I (−17.4 kb) determinant. An unstable hemoglobin (Hb) variant [Hb Adana, codon 59 (C→A)] was present in association with the α‐thal-1 deletion (20.5 kb) in two adults and caused a severe type of Hb H disease. Five patients with Hb H disease had the genotype – –^{MED II}/α^{PA 2}α one had a Hb S heterozygosity (– –^{MED II}/α^{PA 2}α + Hb AS). A patient with Hb H disease (– –^{MED I}/−α^3.7) also had Hb S trait.

Keywords:

• Hb H disease
• α-Thalassemia (thal)
• Hb Adana
• Polyadenylation signal (Poly A)

Notes

*Presented at the Second Titus H.J. Huisman Memorial Symposium, Adana, Turkey, May 8–9, 2006.