血友病A患者凝血因子Ⅷ基因内含子1倒位的检测

Frequency of intron 1 inversion of factor Ⅷ gene in Chinese hemophilia A patients with case report of a female patient with heterozygous intron 1 inversion

目的检测中国血友病A（HA）患者中凝血因子Ⅷ（FⅧ）基因内含子1倒位（inv1）的发生频率，并和国外相关资料相比较，明确部分中国HA患者的发病机制。方法用一期法检测158例无关家系HA患者的FⅧ活性（FⅧ：C），进行HA表型诊断；分别采用长距离和双管多重PCR技术检测内含子22倒位（inv22）和inv1；直接测序法进行FⅧ基因全长序列分析。结果在158例无关家系的HA患者中发现有2例（家系）inv1阳性，检出率为1．26％；对其中1例阳性患者家系进行调查，发现1例罕见女性HA患者为inv1携带者。对女性患者另一条染色体FⅧ基因进行全长测序，未发现有新基因突变。结论inv1在中国HA人群中发生率相对较低。女性HA患者为inv1杂合子，其发病考虑为与X染色体非随机失活有关。

Objective To investigate the frequency of intron 1 inversion （inv1） in FⅧ gene in Chinese hemophilia A （HA） patients and to investigate the mechanism of pathogenesis. Methods Peripheral blood samples were collected from 158 unrelated HA patients, aged 20 （1 -73 ） , including one female HA patient, aged 5, and several family members of a patient positive in inv1. One-stage method was used to assay the FⅧ activity （FⅧ： C）. Long distance PCR and multiple PCR in duplex reactions were used to screen for the intron 22 inversion （inv22） and inv1 of the FⅧ coding gene （F8）. The F8 coding sequence was amplified with PCR and sequenced with an automatic sequencer. Results Two unrelated patients （pedigrees） were detected as inv1 positive with a positive rate of 1.26%. A rare female HA patient with inv1 was also discovered in a positive family （3 HA cases were found in this family and regarded as one case in calculating the total detection rate）. The full length of FⅧ was sequenced, and no other mutation was detected. Conclusion There frequency of FⅧ inv1 is low in Chinese HA patients compared with other populations. Female HA patients are heterozygous for FⅧ inv1 and that may be resulted from nonrandom inactivation of X chromosome.