A novel factor XI gene mutation associated with mild factor XI deficiency in a symptomatic patient.

Congenital factor XI deficiency is a rare condition, in which plasma factor XI levels correlate poorly with the severity of haemorrhage. The condition is typically characterized by post-traumatic bleeding. The factor XI gene is located on chromosome 4 and contains 15 exons. More than 80 mutations have so far been described. We describe a novel mutation in the factor XI gene associated with mild factor XI deficiency. The patient, who is of Irish descent, has a history of post-traumatic bleeding and was found to have a borderline factor XI deficiency. DNA sequence analysis of the factor XI gene revealed a novel T to A mutation at nucleotide 168 resulting in the substitution of the cysteine residue at codon 38 with a stop codon (Cys38STOP). The mutation predicts the premature termination of translation of factor XI mRNA resulting in a truncated, and probably unstable, factor XI protein. The presence of the mutation is consistent with the patient's borderline factor XI deficiency.