title: Serum immunoglobulin G level in patients with lupus nephritis and the effect of treatment with corticosteroids and mycophenolate mofetil.
abstract: BACKGROUND
  Reduced serum IgG level is associated with increased risk of infection. We investigated the circulating IgG level and its determining factors in active lupus nephritis patients treated with corticosteroids and mycophenolate mofetil (MMF).
  
  
  METHODS
  This was a retrospective study on the longitudinal IgG profile in Class III/IV ± V lupus nephritis patients treated with prednisolone and MMF.
  
  
  RESULTS
  46 patients were included. At baseline, 34 (73.9%) patients (Group I) had normal or elevated IgG (1444.0 ± 600.5 mg/dL) while 12 (26.1%) (Group II) had IgG levels (567.8 ± 160.9 mg/dL) below the lower limit of normal. IgG levels at baseline, three, six and 12 months after treatment were 1215.4 ± 649.7 mg/dL, 843.9 ± 347.6 mg/dL, 914.5 ± 362.4 mg/dL and 1034.6 ± 452.5 mg/dL respectively. Treatment with prednisolone and MMF led to a significant drop in IgG after two weeks, reaching a nadir at eight weeks, followed by gradual normalization. Similar changes in IgG were observed in Group I patients but there was non-significant change in Group II within the first 24 weeks. Eighteen (39.1%) patients had low IgG by six months, and only one patient had IgG <300 mg/dL, at both three and six months. IgG level was negatively associated with proteinuria at six months (r = -0.711, p = 0.010). Five of 18 patients with low IgG had infections within the first year, while IgG levels below the lower limit of normal did not increase infection risk (relative risk 1.863; 95% confidence interval 0.466 to 6.818, p = 0.280).
  
  
  CONCLUSIONS
  Reduced IgG occurred in 26% of active lupus nephritis patients and the IgG levels are significantly influenced by the severity of proteinuria. Treatment with prednisolone and MMF does not result in clinically important suppression of IgG.
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: D Y H
authors.initials: DY
authors.lastname: Yap
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: S
authors.initials: S
authors.lastname: Yung
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: M K M
authors.initials: MK
authors.lastname: Ma
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: M M Y
authors.initials: MM
authors.lastname: Mok
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: L P Y
authors.initials: LP
authors.lastname: Kwan
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: G C W
authors.initials: GC
authors.lastname: Chan
authors.affiliation: Division of Nephrology, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong dtmchan@hku.hk.
authors.forename: T M
authors.initials: TM
authors.lastname: Chan
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use*; D000328:Adult; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D008181:Lupus Nephritis / Q000097:blood* / Q000188:drug therapy*; D008297:Male; D009173:Mycophenolic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011239:Prednisolone / Q000627:therapeutic use*; D012189:Retrospective Studies
chemical_list: D000305:Adrenal Cortex Hormones; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D011239:Prednisolone; D009173:Mycophenolic Acid
keywords: Immunoglobulin G; lupus; mycophenolate mofetil; nephritis