Effect of IL6 -174 G/C Gene Polymorphism on Response to Interleukin-6 Blocking Therapy in Systemic Juvenile Idiopathic Arthritis

Abstract

Objective: The main objective of this study was to evaluate the association of IL6-174 G/C gene polymorphisms and the response to tocilizumab (TCZ) in patients with systemic juvenile idiopathic arthritis (s-JIA).
 Methods: Sixty patients with s-JIA (37 males and 23 females with median age at onset of 5.2 years) who received TCZ were recruited. Basic demographic, laboratory and clinical data were collected alongside the IL-6 haplotype status. The overall response to treatment with TCZ was assessed according to a number of variables including the extent of disease activity reduction, the achievement of clinically inactive disease, the necessity to switch to another biologic disease modifying anti-rheumatic drug (bDMARD) and the achievement of a glucocorticoid-free state.
 Results: Three IL6 -174 genotypes, including, GG, GC, and CC were found with higher frequencies of GC genotype. These genotypes had non-significant association with the response of s-JIA patients to IL-6 blockade in this cohort study. However, a longer time frame from disease onset to diagnosis was associated with poorer long-term treatment response.
 Conclusion: We observed no significant impact of IL6 -174 G/C gene polymorphisms on treatment response to TCZ in s-JIA Egyptian patients. The observation that a shorted timeframe between symptom onset and diagnosis is associated with better long-term response to TCZ provides evidence for a therapeutic “window of opportunity” in patients with s-JIA.