Patient population and study design

The sample set consisted of 125 JIA patients followed in two departments (the Rheumatology Unit of the 4th Medical Department of Internal Medicine and the Rheumatology Unit of the 1st Medical Department of Pediatrics) of the Aristotelian University of Thessaloniki Hospital (Thessaloniki, Greece). In this study, only patients who fulfilled the 2001 revised ILAR criteria for JIA were enrolled. Written informed consent was obtained from parents for those patients who were <18 years of age. A total of 221 unrelated healthy individuals, sex- and ethnic-matched selected from the Transfusion Medicine Department of Hippokration Hospital of Thessaloniki, served as controls for the genotyping (14). The study was approved by the local Ethics Committee for medical research and was carried out in compliance with the Declaration of Helsinki.