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Extended report
Efficacy of intravenous Ig therapy in juvenile dermatomyositis
  1. Catherine G Lam1,
  2. Cedric Manlhiot1,
  3. Eleanor M Pullenayegum2,3,
  4. Brian M Feldman4,5,6
  1. 1Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada
  2. 2Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada
  3. 3Centre for Evaluation of Medicines, St Joseph's Healthcare, Hamilton, Ontario, Canada
  4. 4Department of Paediatrics, Division of Rheumatology, Hospital for Sick Children, Toronto, Ontario, Canada
  5. 5Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  6. 6Department of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to Brian M Feldman, Department of Paediatrics, Division of Rheumatology, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; brian.feldman{at}sickkids.ca

Abstract

Intravenous immunoglobulin (IVIg) is an adjunctive therapy for juvenile dermatomyositis (JDM) patients with poor response to first-line therapy (corticosteroid resistant; SR) or who are corticosteroid dependent (SD). Patients requiring IVIg are generally expected to have poorer outcomes, leading to confounding by indication in observational studies. Few studies have evaluated IVIg efficacy in JDM.

Objectives Compared with similar matched controls, to determine if JDM IVIg recipients achieve quiescence sooner and have less disease activity. For SD patients, to determine if IVIg recipients exhibit less disease activity than IVIg-naive patients.

Methods A retrospective inception cohort of 78 JDM patients was studied. Kaplan–Meier survival determined time to quiescence. Marginal structural modelling was used to account for confounding by indication by incorporating inverse probability of treatment weights to handle patients' unequal likelihood of receiving IVIg.

Results While similar demographically, the 30 IVIg patients demonstrated weaker muscle strength and more had photosensitivity at baseline than the 48 controls. As expected, IVIg patients achieved quiescence later than controls in unadjusted analysis. However, although IVIg patients started with greater disease activity, after accounting for confounding as best possible, they maintained similar or lower disease activity than controls from 30 days to 4 years post-diagnosis. This improvement was most marked in SR patients. Among SD patients, IVIg recipients maintained lower disease activity than IVIg-naive patients.

Conclusion This study, involving the largest JDM cohort receiving IVIg to date, applied bias-reduction methods and demonstrated IVIg efficacy in controlling JDM disease activity, particularly for SR patients.

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Footnotes

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the institutional Research Ethics Board of the Hospital for Sick Children, Toronto, Ontario, Canada.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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