HLA II class alleles in juvenile idiopathic arthritis patients with and without temporomandibular joint arthritis

Background: Temporomandibular joint (TMJ) arthritis is seen very often (38-87 %) in children with juvenile idiopathic arthritis (JIA). With contrast enhanced magnetic resonance imaging (MRI) we can detect more cases of TMJ arthritis than ever before. Previous studies show that HLA II class alleles may have protective or risk importance in JIA subtypes. Our objective is to identify HLA II class alleles of risk and protection in JIA patients with TMJ arthritis. Methods: During the period from 2010 to 2015 MRI for TMJ was performed in 85 JIA patients who were genotyped for HLA-DRB1; DQB1 and DQA1 using RT-PCR with sequence-specific primers. As a control group, data of 100 individuals were taken from the genetic bank of RSU Joint Laboratory of Clinical Immunology and Immunogenetics. Associations of DRB1; DQB1; DQA1 alleles in patients were examined individually using the chi(2) test. P-value (<0.05) and odds ratio were calculated using EPI INFO 6.0 software. Results: Out of 85 JIA patients with mean age of 13.7 +/- 3.0 years (range 6.9-17.9 years), 59 (69 %) were girls and 26 (31 %) were boys. The mean duration of the disease was 3.07 +/- 2.35 years (range 0.2-11.0 year). JIA subtypes were as follows: seronegative polyarthritis 51 (60 %), seropositive polyarthritis 6(7 %), oligoarthritis extended 7(8 %), oligoarthritis persistent 2 (2 %) arthritis with enthesitis 14 (17 %), undifferentiated 3 (4 %) and 2 (2 %) systemic arthritis. Two groups where separated after TMJ MRI exam: first with at least two signs of active inflammation and/or any structural damage (n = 62); second with no pathologic signs or with slight contrast enhancement (n = 23). We discovered that there are risk alleles that are found in all JIA patient's groups (MRI positive and negative groups) versus controls such as DRB1*07:01, DQB1*03:03; DQB1*05:01. Also some protective alleles as DRB1*18:01, DQB1*06:02-8 were found in overall JIA group. Alleles DRB1*12:01, DQB1*03:01; DQA1*05:01 were found to be protective for TMJ arthrits. Conclusion: In our study there were no convincing risk alleles, but there are alleles that probably are protective for TMJ arthritis like DRB1*12:01, DQB1*03:01; DQA1*05:01.