title: The autoimmune spectrum of myasthenia gravis: a Swedish population-based study.
abstract: OBJECTIVE
  To determine the prevalence of myasthenia gravis (MG) and the rate of concurrent autoimmune diseases in patients with MG.
  
  
  METHODS
  Using the Swedish health and population registers, during the period 2005-2010, we conducted a nested case-control study of patients with MG (n = 2045) with five age- and sex-matched population-based controls per case. Register-based MG diagnosis was validated against the Stockholm MG Cohort. Similar nested case-control studies were conducted in patients with multiple sclerosis (MS), as a neuroinflammatory disease control, and siblings of patients with MG.
  
  
  METHODS
  Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated as a measure of the association between MG and other autoimmune diseases.
  
  
  RESULTS
  The prevalence of MG was 24.8/100,000, and patients with MG had an increased risk of another autoimmune disease compared to controls (22.0% vs. 8.9%; OR: 2.82, 95% CI: 2.49-3.20); this risk was stronger amongst younger persons and women. Polymyositis/dermatomyositis, systemic lupus erythematosus and Addison's disease, three conditions regulated by the HLA-B8-DR3 haplotype, were most strongly associated with MG, especially early-onset disease. HLA typing in the Stockholm MG Cohort showed that early-onset MG was indeed dominated by HLA-B8-DR3. The risk of another autoimmune disease was increased in both patients with MS and siblings of patients with MG, compared to their respective controls, but to a lesser extent than in patients with MG.
  
  
  CONCLUSIONS
  Our results suggest that MG shares risk factors with other autoimmune diseases, to a greater degree than MS, with a particular role of the HLA-B8-DR3 haplotype, especially amongst younger and female patients.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Fang
authors.forename: O
authors.initials: O
authors.lastname: Sveinsson
authors.forename: G
authors.initials: G
authors.lastname: Thormar
authors.forename: M
authors.initials: M
authors.lastname: Granqvist
authors.forename: J
authors.initials: J
authors.lastname: Askling
authors.forename: I E
authors.initials: IE
authors.lastname: Lundberg
authors.forename: W
authors.initials: W
authors.lastname: Ye
authors.forename: L
authors.initials: L
authors.lastname: Hammarström
authors.forename: R
authors.initials: R
authors.lastname: Pirskanen
authors.forename: F
authors.initials: F
authors.lastname: Piehl
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001327:Autoimmune Diseases / Q000150:complications / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D015795:HLA-B8 Antigen / Q000235:genetics; D006239:Haplotypes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications / Q000453:epidemiology; D010641:Phenotype; D015995:Prevalence; D012307:Risk Factors; D017678:Sex Distribution; D013548:Sweden / Q000453:epidemiology
chemical_list: D015795:HLA-B8 Antigen
keywords: HLA antigens; autoimmune diseases; concomitant disease; myasthenia gravis