title: Antititin antibody in early- and late-onset myasthenia gravis.
abstract: OBJECTIVE
  Myasthenia gravis (MG) is an autoimmune disease caused by antibodies against neuromuscular junction proteins, 85% of patients have antibodies against acetylcholine receptor (AChR-MG). Antititin antibodies are present in a subset of patients with MG. We aimed to determine the value of antititin antibodies as severity markers and thymoma predictors in early- and late-onset MG.
  
  
  METHODS
  Two-hundred and ninety-five consecutive MG patients (188 F and 107 M) aged 12-89 years (mean 50y) were included. 164 patients had early-onset (EOMG, ≤50 years of age), 131 had late-onset MG (LOMG). Twenty-six patients had thymoma. symptoms, severity graded with MGFA scale, thymus histology, medications, and treatment results were analyzed.
  
  
  RESULTS
  Antititin antibodies were present in 81 (27%) of all patients: 54% of thymoma MG, 0.6% of non-thymomatous EOMG, and 55% of LOMG, with proportion of titin-positive patients increasing linearly from 40% in the 6th to 88% in the 9th decade of life. Titin-positive patients had more bulbar symptoms (P = 0.003). Severity of MG, need for immunosuppression, myasthenic crisis risk or treatment results were not related to its presence. Antititin antibodies had 56% sensitivity, 99% specificity, 90% positive predictive value (PPV), and 95% negative predictive value (NPV) for thymoma diagnosis in EOMG, and 50% sensitivity, 75% specificity, 71% PPV and 55% NPV in LOMG.
  
  
  CONCLUSIONS
  Antititin antibodies have high PPV and NPV for thymoma in EOMG. In MG without thymoma, antititin antibodies can be considered as markers of LOMG, but not of a severe course in our MG cohort.
authors.affiliation: Department of Neurology, Medical University of Warsaw, Warsaw, Poland.
authors.forename: P
authors.initials: P
authors.lastname: Szczudlik
authors.forename: B
authors.initials: B
authors.lastname: Szyluk
authors.forename: M
authors.initials: M
authors.lastname: Lipowska
authors.forename: B
authors.initials: B
authors.lastname: Ryniewicz
authors.forename: J
authors.initials: J
authors.lastname: Kubiszewska
authors.forename: M
authors.initials: M
authors.lastname: Dutkiewicz
authors.forename: N E
authors.initials: NE
authors.lastname: Gilhus
authors.forename: A
authors.initials: A
authors.lastname: Kostera-Pruszczyk
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D015415:Biomarkers / Q000097:blood*; D002648:Child; D064211:Connectin / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000097:blood / Q000276:immunology*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D015415:Biomarkers; D064211:Connectin; C577285:TTN protein, human
keywords: antititin antibody; course of myasthenia early onset; late onset; myasthenia gravis; thymoma