Background/Purpose:  Factors affecting treatment (Rx) responses in juvenile dermatomyositis (JDM) are not well understood.  We examined a large JDM registry for predictors of excellent Rx responses, including final discontinuation of corticosteroid therapy (CS-DC), complete clinical response (CCR, clinically inactive disease for ≥6 continuous mths on Rx), and remission (inactive disease for ≥6 continuous mths off all Rx).

Methods: A retrospective review of Rx responses in 305 pts with probable or definite JDM was conducted. The median Rx duration was 30 mths [IQR 19-57 mths] and follow-up duration was 43 mths [IQR 22-74 mths]. We evaluated the probability of achieving CS-DC, CCR, and remission by Weibull time-to-event models. Significant univariable predictors of each outcome (Log rank P<0.05) were examined in multivariable time-to-event analysis using Markov chain Monte Carlo Weibull extension models. The conditional probability of each outcome was also evaluated using Bayesian network models.

Results:  Fifty-two percent (159 pts) experienced final CS-DC and the probability of achieving CS-DC was 9.7% at 1 year, 35% at 3 years and 57% at 5 years after initial Rx. Thirty-three percent (99 pts) achieved CCR and the probability of achieving CCR was 7.9% at 1 year, 27% at 3 years and 44% at 5 years after Rx start. Twenty-six percent (80 pts) achieved remission, including 31 pts who achieved remission without CCR first. The probability of remission was 3.2% at 1 year, 16% at 3 years, and 31% at 5 years after Rx start.  The probability of CCR or remission was found to be conditional: For CCR, the probability of attaining CCR given CS-DC was 47%; when CS-DC was not attained, the probability of achieving CCR was 19%. For remission, when CS-DC and CCR were achieved the probability of achieving remission was 66%. When CS-DC and CCR were not achieved, the probability of achieving remission was 3.5%. If either CS-DC or CCR were achieved in isolation, the probability of achieving remission was 27%.

The absence of calcinosis and infection within 6 months of illness onset were associated with shorter times to achieve these 3 outcomes in multivariable modeling (Table).  The absence of GI, pulmonary or cardiac symptoms was associated with shorter times to achieve CS-DC and CCR. MDA5 Abs and lack of p155/140 Abs, but MJ Abs and lack of early flare were associated with shorter times to CS-DC and CCR, respectively. Achievement of CCR strongly predicted shorter time to remission, with CS-DC, absence of lipodystrophy and younger age at first Rx as other predictors. 

Conclusion:  A large proportion of JDM patients achieve positive Rx responses, including CS-DC, CCR, and remission, although timelines for these important outcomes are relatively long.  Factors associated with shorter times to achieve these Rx outcomes include selected clinical features, MSAs, and environmental factors.