title: Simultaneous genotyping of coagulation factor XI type II and type III mutations by multiplex real-time polymerase chain reaction to determine their prevalence in healthy and factor XI-deficient Italians.
abstract: BACKGROUND
  Factor XI deficiency is a rare autosomal recessive coagulopathy, which is, however, common among Ashkenazi Jews, in whom the so-called type II (E117X) and type III (F283L) mutations account for 98% of alleles. In non-Jewish populations, a higher level of allelic heterogeneity has been reported. However, the type II mutation was found in individuals from England, Portugal, and Italy, and haplotype analysis confirmed its Jewish origin. The aims of this study were to develop a rapid and accurate assay for the simultaneous detection of type II/type III mutations and to determine the frequency of these mutations in a large Italian population of healthy individuals and in a cohort of factor XI-deficient Italian patients.
  
  
  METHODS
  Type II and III mutations were detected using a newly developed multiplex four-color real-time polymerase chain reaction assay. Haplotype analysis was performed by either DNA sequencing or fragment-length analysis.
  
  
  RESULTS
  Both type II and type III mutations were found among 3879 healthy Italians with an allele frequency of 0.00064 and 0.00051, respectively. Among the 31 analyzed factor XI-deficient patients, the type II mutation was found in three individuals in the homozygous state and in eight individuals in the heterozygous state (one compound heterozygote type II/III). Haplotype analysis revealed the Jewish origin of both mutations.
  
  
  CONCLUSIONS
  The newly developed assay is highly specific and reliable (0.02% false positives); and offers a useful means for the molecular diagnosis of factor XI deficiency. Type II and III mutations are present in the Italian population and should be searched for first in factor XI-deficient patients.
authors.affiliation: Department of Biology and Genetics for Medical Sciences, via Viotti 3/5, 20133 Milan, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Zadra
authors.forename: Rosanna
authors.initials: R
authors.lastname: Asselta
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Tenchini
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Castaman
authors.forename: Uri
authors.initials: U
authors.lastname: Seligsohn
authors.forename: Pier Mannuccio
authors.initials: PM
authors.lastname: Mannucci
authors.forename: Stefano
authors.initials: S
authors.lastname: Duga
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005172:Factor XI / Q000235:genetics*; D005173:Factor XI Deficiency / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009154:Mutation; D015995:Prevalence; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D005172:Factor XI