title: What are the characteristics of asthma patients with elevated serum IgG4 levels?
abstract: BACKGROUND
  IgG4 has recently been a subject of great interest in human pathology. No data are available about the characteristics of asthma patients with elevated IgG4 levels.
  
  
  METHODS
  An observational study was conducted from January 2006 to March 2015 in a difficult-to-treat population of asthma patients. Twenty-six difficult-to-treat asthma patients with elevated serum IgG4 levels (IgG4/IgG ratio up to 10%) were compared with a control population of 98 difficult-to-treat asthma patients with normal serum IgG4. Blood eosinophilia, total IgE and FeNO were compared between groups to better characterize asthma patients with elevated serum IgG4 levels.
  
  
  RESULTS
  Median IgG4 concentrations were 1.72 g/l [1.19-2.36] and 0.22 g/l [0.10-0.49] in the elevated IgG4 group and normal Ig4 group, respectively. Median blood eosinophilia was more than three times higher in patients with elevated serum IgG4 levels than in controls (0.75 10(9)/L [IQR 0.54-1.78] vs 0.22 10(9)/L [IQR 0.09-0.54] respectively, p < 0.0001). Total IgE was twice as high (264.5 kUI/l [IQR 166.3-779] vs 126 kUI/l [IQR 26-350] respectively; p < 0.05) and FeNO was nearly twice as high (61 [IQR 41-111] ppb vs 35 [IQR 23-51] ppb, p < 0.001). Allergic broncho-pulmonary aspergillosis (ABPA) and eosinophilic granulomatosis with polyangiitis (EGPA) were observed in the asthma patients with elevated serum IgG4. Ten patients had unexplained increased blood eosinophilia.
  
  
  CONCLUSIONS
  Asthma patients with elevated IgG4 levels have significantly higher blood eosinophilia, total IgE and FeNO. ABPA and EGPA are observed in patients with elevated serum IgG4.
authors.affiliation: CHRU Tours, Service de Pneumologie, F-37044 Tours, France.
authors.forename: T
authors.initials: T
authors.lastname: Flament
authors.affiliation: CHRU Tours, Service de Pneumologie, F-37044 Tours, France; Université François Rabelais, UMR 1100, F-37032 Tours, France; INSERM, Centre d'Etude des Pathologies Respiratoires, UMR 1100/EA6305, F-37032 Tours, France.
authors.forename: S
authors.initials: S
authors.lastname: Marchand-Adam
authors.affiliation: CHRU Tours, Service de néphrologie, F-37044 Tours, France.
authors.forename: P
authors.initials: P
authors.lastname: Gatault
authors.affiliation: CHRU Tours, Service de Pneumologie, F-37044 Tours, France.
authors.forename: C
authors.initials: C
authors.lastname: Dupin
authors.affiliation: CHRU Tours, Service de Pneumologie, F-37044 Tours, France; Université François Rabelais, UMR 1100, F-37032 Tours, France; INSERM, Centre d'Etude des Pathologies Respiratoires, UMR 1100/EA6305, F-37032 Tours, France.
authors.forename: P
authors.initials: P
authors.lastname: Diot
authors.affiliation: CHRU Tours, Service de Pneumologie, F-37044 Tours, France; Université François Rabelais, UMR 1100, F-37032 Tours, France; INSERM, Centre d'Etude des Pathologies Respiratoires, UMR 1100/EA6305, F-37032 Tours, France. Electronic address: laurent.guilleminault@univ-tours.fr.
authors.forename: L
authors.initials: L
authors.lastname: Guilleminault
mesh_terms: D000328:Adult; D000368:Aged; D001229:Aspergillosis, Allergic Bronchopulmonary / Q000453:epidemiology / Q000276:immunology*; D001249:Asthma / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D001944:Breath Tests; D015267:Churg-Strauss Syndrome / Q000453:epidemiology / Q000276:immunology*; D015331:Cohort Studies; D004802:Eosinophilia / Q000453:epidemiology / Q000276:immunology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D012189:Retrospective Studies; D014797:Vital Capacity
chemical_list: D007074:Immunoglobulin G; D009569:Nitric Oxide; D007073:Immunoglobulin E
keywords: Allergic broncho-pulmonary aspergillosis; Asthma; Eosinophilic granulomatosis with polyangiitis; IgG4