[Detection of intron 22 inversion of factor VIII gene in severe hemophilia A patients]

To investigate the incidence of intron 22 inversion (INV22) of factor VIII (FVIII) gene in severe hemophilia A (HA) patients, clarify its pathological mechanism, and identify INV22 carrier in the female family members.

One-stage method was used to assay the FVIII activity (FVIII:C)in 126 severe HA patients with a median age of 14 years old (range: 4 months-63 years). INV22 was analyzed by long-distance polymerase chain reaction (LD-PCR) and pulsed field gel electrophoresis (PFGE), and pedigree were conducted in 3 involved HA families.

Of all the 126 severe HA, 52 (41.3%) cases had the INV22. Four females including 3 mothers and 1 sister of probands were diagnosed as INV22 carriers among 11 suspected carrier mosaicisms from 3 INV22 positive HA families. In 8 females from one family without HA history, the patient's mother was a INV22 carrier, but her maternal grandmother, 2 maternal aunts, 2 female siblings and 1 elder female cousin were negative.

LD-PCR and PFGE could be used to diagnose severe HA patients with INV22 and identify the carriers.