Elevated serum interferon‐α activity in juvenile dermatomyositis: Associations with disease activity at diagnosis and after thirty‐six months of therapy

Abstract

Objective Interferon‐α (IFNα) has been implicated in the pathogenesis of juvenile dermatomyositis (DM). The aim of this study was to examine serum IFNα activity in a cohort of children with juvenile DM to determine relationships between IFNα and indicators of disease activity and severity. Methods Thirty‐nine children with definite/probable juvenile DM were included in the study. Serum samples were obtained at the time of diagnosis from 18 untreated patients with juvenile DM. Second samples from 11 of these patients were obtained at 24 months, while they were receiving treatment, and third samples were obtained from 7 of these patients at 36 months. The remaining 21 children were studied 36 months after their initial diagnosis. Serum IFNα activity was measured using a functional reporter cell assay. Results Patients with juvenile DM had higher serum IFNα activity than both pediatric and adult healthy control subjects. In untreated patients, serum IFNα activity was positively correlated with serum muscle enzyme levels (P < 0.05 for creatine kinase, aspartate aminotransferase, and aldolase) and inversely correlated with the duration of untreated disease (P = 0.017). The tumor necrosis factor α −308A allele was associated with higher serum IFNα levels only in untreated patients (P = 0.030). At 36 months, serum IFNα levels were inversely correlated with muscle enzyme levels in those patients still requiring therapy and with the skin Disease Activity Score in those patients who had completed therapy (P = 0.002). Conclusion Serum IFNα activity was associated with higher serum levels of muscle‐derived enzymes and a shorter duration of untreated disease in patients with newly diagnosed juvenile DM and was inversely correlated with measures of chronic disease activity at 36 months postdiagnosis. These data suggest that IFNα could play a role in disease initiation in juvenile DM.