title: Geographical Distribution of Myasthenia Gravis in Northern Europe--Results from a Population-Based Study from Two Countries.
abstract: OBJECTIVE
  To compare the prevalence of myasthenia gravis (MG) subgroups based on immunological markers and clinical presentation in two geographically complete MG populations in northern Europe.
  
  
  METHODS
  This cross-sectional study included all living MG patients in Norway and a regional cohort from the Netherlands. Patients were identified using their hospital registration codes. Medical charts of subjects >16 years were reviewed. Inclusion criteria were clinical MG, a positive antibody test for acetylcholine receptor (AChR MG) or muscle-specific kinase (MuSK MG), or if seronegative MG, confirmed by an electrophysiological test.
  
  
  RESULTS
  1,205 MG patients (534 Norwegians and 671 Dutch) fulfilled the criteria, giving a higher point prevalence in the Netherlands (167/million, 95% CI 155-180) than in Norway (138/million, 95% CI 126-150). In particular, rates of AChR MG (143 vs. 111/million), MuSK MG (6.5 vs. 0.5/million), and ocular phenotype (62 vs. 24/million) were higher in the Netherlands.
  
  
  CONCLUSIONS
  Novel findings are an AChR MG geographical north-south gradient and a 2.6-fold more ocular MG patients in the Netherlands than in Norway. The MuSK MG latitudinal gradient supports the notion of a north-south gradient in Europe, with a higher prevalence in the south. The variation is probably explained by genetic differences between the populations, in addition to environmental interactions.
authors.affiliation: Department of Neurology, Oslo University Hospital, Ullevål and Rikshospitalet, Oslo, Norway.
authors.forename: Marion I
authors.initials: MI
authors.lastname: Boldingh
authors.forename: Angelina H
authors.initials: AH
authors.lastname: Maniaol
authors.forename: Cathrine
authors.initials: C
authors.lastname: Brunborg
authors.forename: Luuk
authors.initials: L
authors.lastname: Dekker
authors.forename: Anne T
authors.initials: AT
authors.lastname: Heldal
authors.forename: A F
authors.initials: AF
authors.lastname: Lipka
authors.forename: Trine H
authors.initials: TH
authors.lastname: Popperud
authors.forename: Erik H
authors.initials: EH
authors.lastname: Niks
authors.forename: J J G M
authors.initials: JJ
authors.lastname: Verschuuren
authors.forename: Chantal M E
authors.initials: CM
authors.lastname: Tallaksen
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000453:epidemiology*; D010641:Phenotype; D012737:Sex Factors; D055815:Young Adult