Response to Etanercept in Juvenile Idiopathic Arthritis

Abstract

in Juvenile Idiopathic Arthritis To the Editor: The study presented by Dr Otten and colleagues assessed factors associated with treatment response to etanercept in patients with juvenile idiopathic arthritis (JIA). They found that approximately one-third of the patients with JIA achieved an excellent response, which was associated with low baseline disability scores, low numbers of disease-modifying antirheumatic drugs used before initiating etanercept, and younger age at onset of JIA. Onethird achieved a poor response, which was associated with systemic JIA and female sex. However, we think that their conclusions are problematic because differences between systemic JIA and other types exist in terms of intrinsic etiology and pathogenesis. Information about the immune pathogenesis of JIA discovered in the past 5 years has confirmed that systemic JIA is a different disease from other types of JIA and should be treated as an acquired autoinflammatory disease. Juvenile idiopathic arthritis is not only a heterogeneous group of diseases characterized by arthritis of unknown origin with onset before the age of 16 years but also a diagnosis of exclusion, which is made only when other causes such as congenital joint deformity, neurovascular disorder, trauma, and infection have been ruled out. The discrepancies in treatment response in Otten et al’s study also suggest that the diagnosis of JIA encompasses different categories with different etiologies and pathogenesis, so the major factor associated with treatment response to etanercept in JIA may be the type rather than sex or age. Thus, the comparison of treatment response between systemic JIA and other categories may not be helpful; the comparison with greater significance for clinical practice would be a comparison within types—systemic or nonsystemic.