title: MuSK-positive myasthenia gravis is rare in the Polish population.
abstract: OBJECTIVE
  MuSK-positive myasthenia gravis (MG) is diagnosed in 0-48% of cases with generalized seronegative MG in different populations. The presence of anti-MuSK antibodies generally relates to a severe course and lack of response to thymectomy. We analyzed for the first time the serology and clinical characteristics of MuSK-positive MG in the Polish population.
  
  
  METHODS
  One hundred and fifty-one patients were tested for the presence of anti-AChR and anti-MuSK antibodies: 62 with seronegative MG, including 14 with ocular seronegative MG, 48 age-matched patients with seropositive MG and 41 controls.
  
  
  RESULTS
  All patients with seropositive MG and the disease controls were MuSK-negative. Anti-MuSK antibodies were detected only in four patients with seronegative MG (8.7% of generalized seronegative cases): three women and one man. All four had predominantly bulbar involvement, and underwent thymectomy, with no apparent benefit. All of them improved clinically after immunosuppressive treatment with remissions lasting up to 7 years.
  
  
  CONCLUSIONS
  MuSK-positive MG is rare in Polish population accounting for only 8.7% of seronegative cases with generalized MG. This is consistent with emerging evidence for lower MuSK antibodies at more northerly latitudes.
authors.affiliation: Department of Neurology, Medical University of Warsaw, Warsaw, Poland. akostera@amwaw.edu.pl
authors.forename: A
authors.initials: A
authors.lastname: Kostera-Pruszczyk
authors.forename: A
authors.initials: A
authors.lastname: Kamińska
authors.forename: M
authors.initials: M
authors.lastname: Dutkiewicz
authors.forename: B
authors.initials: B
authors.lastname: Emeryk-Szajewska
authors.forename: M H
authors.initials: MH
authors.lastname: Strugalska-Cynowska
authors.forename: A
authors.initials: A
authors.lastname: Vincent
authors.forename: H
authors.initials: H
authors.lastname: Kwieciński
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000097:blood*; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D009157:Myasthenia Gravis / Q000097:blood / Q000276:immunology* / Q000628:therapy; D011044:Poland / Q000453:epidemiology; D015995:Prevalence; D011863:Radioimmunoassay; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D013934:Thymectomy
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D007166:Immunosuppressive Agents; D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases