Cai X-H, Wang X-F, Dai J, Fang Y, Ding Q-L, Xie F, Wang H-L
Blood Transfusion Department, Ruijin Hospital, Medical College of Shanghai Jiao Tong University, Shanghai, China.
J Thromb Haemost. 2006 Sep;4(9):1969-74. doi: 10.1111/j.1538-7836.2006.02105.x. Epub 2006 Jun 27.
Hemophilia A (HA) is an X-chromosome-linked recessive disorder.
We report the case of a female HA patient with a moderate decrease of factor (F) VIII activity and antigen (FVIII:C 3.4%, FVIII:Ag 4.2%) and severe bleeding symptoms.
The patient's father had mild FVIII deficiency (FVIII:C 6.9%, FVIII:Ag 7.4%), and her mother had normal FVIII activity. The von Willebrand disease antigen and von Willebrand factor ristocetin cofactor activity were normal in all family members. The genomic DNA was extracted from the peripheral blood lymphocytes of the patient and her family members. Long-distance polymerase chain reaction (PCR) was employed to screen for the intron 22 inversion of the FVIII coding gene (F8). The F8 coding sequence was amplified with PCR and sequenced with an automatic sequencer.
Two heterozygous mutations were identified in the patient: one a substitution of nucleotide 5981T by C that leads to a missense mutation Leu1975Pro, and the other an insertion of an 'A' between nucleotides 3,637 and 3,638 (3637_3638insA) that shifts the reading frame and predicts a premature stop codon downward. The mutation Leu1975Pro was identified in the father's F8; however, 3637_3638insA was a de novo mutation that occurred in the patient's maternal-derived F8. Real-time PCR was applied to analyze the level of ectopically F8 gene transcripts in the peripheral lymphocytes of family members. The ectopic transcripts of F8 of the patient were less abundant than the normal control (patient:normal control ratio 0.67), whereas her parents showed no significant difference from the normal control.
The FVIII deficiency of the HA patient resulted from a de novo occurrence of a frameshift 3637_3638insA in her maternal-derived F8 and a novel missense mutation Leu1975Pro inherited from her father.
甲型血友病（HA）是一种X染色体连锁隐性疾病。
我们报告一例女性HA患者，其因子（F）VIII活性和抗原中度降低（FVIII:C 3.4%，FVIII:Ag 4.2%），并有严重出血症状。
患者的父亲有轻度FVIII缺乏（FVIII:C 6.9%，FVIII:Ag 7.4%），其母亲FVIII活性正常。所有家庭成员的血管性血友病因子抗原和血管性血友病因子瑞斯托霉素辅因子活性均正常。从患者及其家庭成员的外周血淋巴细胞中提取基因组DNA。采用长距离聚合酶链反应（PCR）筛选FVIII编码基因（F8）的内含子22倒位。用PCR扩增F8编码序列，并用自动测序仪进行测序。
在患者中鉴定出两个杂合突变：一个是核苷酸5981T被C取代，导致错义突变Leu1975Pro；另一个是在核苷酸3637和3638之间插入一个“A”（3637_3638insA），使阅读框移位，并预测向下出现提前终止密码子。Leu1975Pro突变在父亲的F8中被鉴定出来；然而，3637_3638insA是一个新发突变，发生在患者母源的F8中。应用实时PCR分析家庭成员外周淋巴细胞中异位F8基因转录本的水平。患者F8的异位转录本比正常对照少（患者:正常对照比值0.67），而其父母与正常对照无显著差异。
该HA患者的FVIII缺乏是由于其母源F8中出现新发的移码突变3637_3638insA以及从父亲遗传而来的新错义突变Leu1975Pro所致。
