OBJECTIVEHemophilia A is an inherited bleeding disorder caused by defects in factor VIII (FVIII) gene. In the present study, the frequencies of the microsatellite alleles at introns 13 and 22 in the factor VIII gene were analyzed in the group of Han nationality in Guangxi Zhuang Autonomous Region to explore their diagnostic value for hemophilia A. These two sites were also used to detect the carriers in 13 hemophilia A families.

METHODSNinty-one individuals of Han ethnic group in Guangxi Zhuang Autonomous Region (135 X chromosomes) and 13 HA families were subjected to molecular studies. First, these two fragments were PCR amplified simultaneously. Then, silver staining was used later to show their polymorphisms. The investigators selected one sample at random to obtain its lengths of the PCR products at these two sites by ABI310 PCR amplifier. After counting its repeated numbers of (CA) according to the documents concerned, the repeated numbers of the other samples could be counted easily.

RESULTSIn the 91 individuals, 6 and 4 alleles were detected at these two sites, respectively. At intron 13 the allele frequencies ranged from 0.0002 to 0.5408 and polymorphism information content (PIC) was 0.5899. At intron 22 the allele frequencies ranged from 0.0444 to 0.4963 and its PIC was 0.5359. The actual heterozygosity for intron 13 and intron 22 were 0.6364 (28/44) and 0.5227 (23/44), respectively. In 13 hemophilia A families with positive history, 9 of them were diagnosed by this method and the diagnosis rate was 69%.

CONCLUSIONWith high PICs, (CA)n at intron 13 and intron 22 were two valuable sites in the diagnosis of hemophilia A in the population of Han ethnic group in Guangxi Zhuang Autonomous Region. Compared with some other HA restrictive fragment length polymorphisms (RFLP), intron 22 (GT)n (AG)n was more informative.