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.
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.
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.
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.
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.