OBJECTIVETo explore factor IX gene mutations and molecular mechanism of haemophilia B in 3 unrelated families.

METHODSThe activated partial thromboplastin time (APTT) and FIX activity (FIX: C) assay were used for phenotypic diagnosis. The STR loci gene polymorphisms for genetic linkage analysis in the patients and their family members were assayed. All of the 8 exons and the exon-intron boundaries of FIX gene were amplified by polymerase chain reaction (PCR) and direct sequencing.

RESULTS AND CONCLUSIONMutations were found in the FIX gene of the propositi. Proband 1 had a G22119A mutation in exon 6, proband 2 a G7392C mutation in exon 2 and proband 3 a T32685C mutation in exon 8.