Different Autoantibody Phenotypes in Juvenile and Adult Myositis Save

A Kyoto University study compared juvenile-idiopathic inflammatory myopathy (IIM) and adult-IIM patients, demonstrating different autoantibody profiles and a more favorable outcome for n juvenile-IIM patients.

This retrospective 20 year study analyzed in 320 Japanese IIM patients (juvenile-IIM, n = 34); adult-IIM, n = 286) from the Kyoto University Registry.

Autoantibodies were different between the two groups: 

• Juvenile-IIM 
  • anti-TIF1-γ  15 %
  • anti-MDA-5  15 %
  • anti-ARS  9%
  • anti-NXP-2  6%. 
• Adult-IIM 
  • anti-ARS 32%
  • anti-MDA-5 23%
  • anti-TIF1-γ 8%
  • anti-SRP 8%
  • anti-Mi-2 2%
  • anti-NXP-2 1%

A drug-free state was more frequently achieved with juvenile-IIM vs adult-IIM (34 % vs. 18 %, p = 0.0016). 

Anti-TIF1-γ was associated with less muscle symptoms (60 % vs. 90 %), malignancy (0 % vs. 57 %), and glucocorticoid use (40 % vs. 86 %) in juvenile-IIM compared to adult-IIM.

Both juvenile-IIM and adult-IIM with anti-MDA-5 manifested a high frequency of amyopathic dermatomyositis, interstitial lung disease (ILD), and multi-immunosuppressive therapy. 

Both juvenile-IIM and adult-IIM with anti-ARS showed frequent skin rashes, muscle symptoms, and ILD, frequent need for multi-immunosuppressive therapy, and low drug-free condition rates (0 % vs. 3 %). 

Both juvenile-IIM and adult-IIM with anti-NXP-2 showed frequent skin rashes and muscle symptoms, low ILD frequency.