title: Origin of mutation in sporadic cases of severe haemophilia A in Sweden.
abstract: Many newly diagnosed Swedish severe haemophilia A (HA) patients are sporadic cases. Some genotypically non-carrier mothers have gone on to have two descendants with the same mutation, presumably because of mosaicism.
  
  
  
  To define the origin of mutation in sporadic cases of HA, reveal possible sex-specific differences in mutagenesis and identify potential mosaics among non-carrier mothers.
  
  
  
  Sanger sequencing characterized the mutations and microsatellite haplotyping determined the origin of the X chromosome carrying the mutation in 3 generations of 45 families with sporadic severe HA. Droplet digital polymerase chain reaction (ddPCR) was used in five cases to reveal that mosaicism mutations are not found on conventional DNA sequencing.
  
  
  
  In 23 out of 45 families, the mother carried the mutation and in 5 out of 28 families, the grandmother was also a carrier. The X chromosome was of grandpaternal origin in 17 out of 23 cases. One of five tested mothers was a mosaic with a mutation frequency of 7%.
  
  
  
  In 40 out of 45 families, the sporadic case resulted from a mutation in the last two generations. In 82% (23/28), the carrier mothers had a de novo mutation where the X chromosome was of paternal origin in 74% (17/23). ddPCR is a potentially powerful and promising analysis for mosaicism in HA.
authors.affiliation: Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.|Department of Paediatrics and Malmö Centre for Thrombosis and Haemostasis, Skåne University Hospital, Lund University, Malmö, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Mårtensson
authors.affiliation: Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Ivarsson
authors.affiliation: Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.|Department of Paediatrics and Malmö Centre for Thrombosis and Haemostasis, Skåne University Hospital, Lund University, Malmö, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Letelier
authors.affiliation: Biomedicine, Kristianstad University, Kristianstad, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Manderstedt
authors.affiliation: Biomedicine, Kristianstad University, Kristianstad, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Halldén
authors.affiliation: Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.|Department of Paediatrics and Malmö Centre for Thrombosis and Haemostasis, Skåne University Hospital, Lund University, Malmö, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Ljung
mesh_terms: D000328:Adult; D002648:Child; D041321:Chromosomes, Human, X / Q000737:chemistry*; D004252:DNA Mutational Analysis; D005260:Female; D056426:Genetic Loci; D006239:Haplotypes; D006467:Hemophilia A / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D006579:Heterozygote; D006801:Humans; D040582:Inheritance Patterns; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D009030:Mosaicism; D009154:Mutation; D010375:Pedigree; D016133:Polymerase Chain Reaction / Q000379:methods; D012720:Severity of Illness Index
keywords: carrier; factor VIII; haemophilia A; mosaicism; mutation; sporadic