P022 Genetic background predicts the extra-articular involvement in patients with enthesitis related arthritis
Authors: Ferjani Hanene , Ines Cherif , Maatallah Kaouther , Triki Wafa , Ben Nessib Dorra , Kaffel Dhia , Hamdi Wafa 
Published: November 2021

Abstract

Background
Enthesitis-related arthritis (ERA) represents 20% of all juvenile idiopathic arthritis subtype. Among the genetic risk factors for the development of ERA, HLA-B27 has been implicated as a major contributor. The frequency of HLA-B27 varies among population. HLA-B 27 status in ERA may influence the clinical phenotype and prognosis of the disease. The main objective of this study is to determine whether genetic background including HLA B27 and familial history of spondylarthritits (SpA) may influence the clinical features of ERA patients.

Methods
We conducted a retrospective study including patients with ERA, all fulfilling the International League of Associations for Rheumatology (ILAR) criteria.
For all patients, we collected the following data: Age, family history of rheumatic inflammatory diseases, inflammatory bowel diseases (IBD), the presence of HLA-B27 antigen, the inflammatory biomarkers: Erythrocyte sedimentation rate (ESR) C-reactive protein (CRP), the disease activity assessed by morning stiffness, night awakenings, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the current treatment. We assessed, as well, the functional impact using the Bath Ankylosing Spondylitis Functional Index (BASFI) the Lequesne index.
The population was divided into two groups: a group including patients positive to HLA-B27 antigen and/or with family history of rheumatic inflammatory diseases, psoriasis or inflammatorybowel diseases. The second group was defined as control group with patients negative to HLA-B27 antigen and without any family history of the diseases above.

Results
We included 40 ERA patients, mean age of onset 12,43 ± 3,003 years (6–16). The majority of them were male (n = 34). Twenty-eight patients had a genetic background. Among them, 7,5% of patients had a positive family history, 42,5% were positive to HLA-B27 antigen and 20% of them met both criteria.
As shown in table 1, clinical manifestations were similar between the 2 groups. Enthesitis was more frequent in patients with HLAB27 without a significant difference. Regarding the disease activity, the number of night awakenings and the morning stiffness duration were comparable in the two groups. Six patients had a BASDAI score &gt; 4 with no difference between the two groups. Extra-articular manifestations were present in 15 patients. Among them 14 had a genetic background, reaching the significance threshold with P = 0,013. We counted 8 cases of uveitis, one case of IBD, 5 cases of lung disease and 1 case of cardiac involvement.
Inflammatory markers were higher in the group with familial history of SpA and/or positive HLAB27. Indeed, the mean ESR value was 42,73 vs 29.9, P = 0,01.
There were no correlations between BASFI score and a positive genetic background (P = 0,283). Only one patient was put on biologics. He has no family history and is negative to HLA-B27 antigen.

Conclusion
The frequency of HLAB27 was in line with the literature data. The genetic background did not influence the disease activity or the functional impairment in our population. However, a positive correlation was found between a positive familial history of SpA, HLAB27, and the presence of extra-articular manifestations as well as with a higher ESR value.