A laboratory strategy for genotyping haemoglobin H disease in the Chinese.

BACKGROUND: The thalassaemias are the commonest blood disorders worldwide, with South East Asia and southern China as areas of high prevalence. Accurate diagnosis of these disorders helps in clinical management with improved outcome. METHODS: The alpha-globin genotypes of 100 Chinese patients in Hong Kong with haemoglobin H (Hb H) disease were characterised. Single-tube multiplex gap-PCR was used to detect --(SEA), -alpha(3.7) and -alpha(4.2), while Hb CS, Hb QS and codon 30 (DeltaGAG) were identified by single-tube multiplex amplification refractory mutation system (ARMS). Automated direct nucleotide sequencing of the amplified alpha2- and alpha1-globin genes was performed to characterise other non-deletional alpha-thalassaemia determinants. RESULTS: In the 100 cases studied, 99 cases had --(SEA) in combination with deletional alpha(+)-thalassaemia or non-deletional alpha-globin gene mutation involving the alpha2-globin gene. In 70 cases of the deletional form, 43 cases showed the genotype of (--(SEA)/-alpha(3.7)) and 27 cases of (--(SEA)/-alpha(4.2)). Three of the 27 cases of (--(SEA)/-alpha(4.2)) were found to have Hb Q-Thailand linked in-cis with -alpha(4.2). The remaining 30 cases were of non-deletional form with the following genotypes: 11 cases of (--(SEA)/alpha(HbCS)alpha), 9 cases of (--(SEA)/alpha(HbQS)alpha), 3 cases of (--(SEA)/alpha(cd30 (DeltaGAG))alpha), 3 cases of (--(SEA)/alpha(cd31)alpha), 2 cases of (--(SEA)/alpha(poly-A)alpha), 1 case of (--(SEA)/alpha(HbWestmead)alpha) and 1 case of (--(non-SEA)/alpha(HbQS)alpha). CONCLUSIONS: Based on two rapid diagnostic tests, multiplex gap-PCR and multiplex ARMS, more than 90% of the cases were genetically characterised. This laboratory strategy should be widely applicable for genetic diagnosis of alpha-thalassaemia.

Molecular characterization of Hb Val de Marne [alpha133(H16)Ser-->Arg; AGC-->AGA; (alpha2)] in a Chinese family.

There have been two previous reports on Hb Val de Marne (Hb Footscray) [alpha133(H16)Ser-->Arg] in the literature, but the molecular characterization has hitherto not been described. Based on the Ser-->Arg transition, the presumed mutation was cited as AGC-->CGC of the alpha2- or alpha1-globin gene. We have found this variant in a 15-year-old Chinese girl and her father, and automated DNA sequencing revealed an AGC-->AGA mutation at codon 133 of the alpha2-globin gene. Since an increasing number of alpha-globin gene variants have been reported with the same protein alteration but with different mutations on the alpha1- or alpha2-globin genes, the mutation identified in the present family does not preclude the presence of other alpha-globin gene mutations leading to this hemoglobin (Hb) variant.