This study concerned the identification of the beta-thalassaemia mutations that were present in 27 Malay patients with Hb E-beta-thalassaemia and seven Malay patients with thalassaemia major who were from West Malaysia. Nearly 50% of all beta-thalassaemia chromosomes carried the G----C substitution at nucleotide 5 of IVS-I; the commonly occurring Chinese anomalies such as the frameshift at codons 41 and 42, the nonsense mutation A----T at codon 17, the A----G substitution at position -28 of the promoter region, and the C----T substitution at position 654 of the second intron, were rare or absent. Two new thalassaemia mutations were discovered. The first involves a frameshift at codon 35 (-C) that was found in two patients with Hb E-beta zero-thalassaemia and causes a beta zero-thalassaemia because a stop codon is present at codon 60. The second is an AAC----AGC mutation in codon 19 that was present on six chromosomes. This substitution results in the production of an abnormal beta chain (beta-Malay) that has an Asn----Ser substitution at position beta 19. Hb Malay is a 'Hb Knossos-like' beta +-thalassaemia abnormality; the A----G mutation at codon 19 likely creates an alternate splicing site between codons 17 and 18, reducing the efficiency of the normal donor splice site at IVS-I to about 60%.
The overseas Chinese in West Malaysia are almost exclusively from the south-eastern provinces of China-Kwangtung, Fukien, and Kwangsi. To institute a comprehensive thalassaemia control programme for this region we have characterised the beta thalassaemia mutations in 16 Chinese patients from West Malaysia: 4 beta thalassaemia mutations were seen: a) an A----G substitution in the TATA box [-28 base pairs (bp)], an A----T substitution in codon 17 [17 A----T], c) a 4 base pairs - TCTT deletion in codon 41-42 [frameshift mutation (FSC 41-42)], and d) a C----T substitution at the second intervening sequence (IVS 11) position 654. Similar mutations have been described in patients from the south-eastern provinces of China. The delineation of the specific mutations present will enable effective prenatal diagnosis for beta thalassaemia of ethnic Chinese in West Malaysia to be instituted.