Factor VII Toyama (Thr 359 Met): a homozygous missense mutation causing severe type I deficiency.

We performed a DNA analysis on a patient with severe type I factor VII deficiency by the polymerase chain reaction amplification and a direct DNA sequencing method. The proband was a 66-year-old Japanese woman who had recurrent episodes of excessive bleeding after dental extraction. The functional and antigenic levels of plasma factor VII markedly reduced to 1.6% and 2% of normal, respectively. However, she had no serious symptoms such as intracranial or intraarticular hemorrhage. The analysis revealed that the patient was homozygous for a missense mutation, Thr (ACG) to Met (ATG) at codon 359 in the catalytic domain. Her deceased parents were first cousins, and their consanguineous marriage presumably resulted in the homozygosity in her. This patient was the first case of homozygote for the Thr359Met mutation, though heterozygotes for the mutation were previously found in an Italian family.