Introduction: Haemoglobin (Hb) G-Philadelphia mutation is a common alpha-globin chain variant [α68(E17)Asn > Lys]. Combined high performance liquid chromatography (HPLC) and isoelectric focusing (IEF) can be used in a presumptive diagnosis of Hb G-Philadelphia, but there are other α-chain variants with a similar phenotype that cannot be excluded. Our aim was to develop a novel StyI restriction enzyme assay to diagnose the common Hb G-Philadelphia mutation and to identify any other variants with a similar phenotype by DNA sequencing.
Methods: Thirty-one cases given a presumptive diagnosis as Hb G-Philadelphia by HPLC and IEF were subjected to DNA analysis by restriction enzyme digestion using StyI. Negative cases were then subjected to DNA sequencing.
Results: Twenty-two cases (78.6%) of 28 cases amplified were tested positive for Hb G-Philadelphia by StyI restriction digestion. Sequencing of the six negative cases revealed two cases of Hb G-Philadelphia with C→A mutation in codon 68 in α2 globin gene, plus one case each of Hb G-Norfolk Hb Stanleyville-II, Hb Matsue-Oki and Hb Mizushi.
Conclusion: A novel StyI restriction enzyme can be used to confirm the commonest type of Hb G-Philadelphia. DNA sequencing identified four other α-chain variants with a similar HPLC and IEF phenotype.
© 2011 Blackwell Publishing Ltd.