ESPE Abstracts

Background: Autoimmune thyroiditis, which can occur in chronic arthritis, involves the immune system attacking the thyroid gland, potentially causing hypothyroidism or hyperthyroidism. However, data on thyroid involvement in Still's disease remains limited, highlighting a significant gap in understanding the full spectrum of autoimmune and autoinflammatory interactions in this condition.

The study aims: to examine the differences between autoinflammatory and autoimmune arthritis in terms of hormonal and autoimmune thyroid changes.

Material and Methods: Ninety patients with juvenile idiopathic arthritis were included, with 45 in the prepubertal group and 45 in the pubertal group. Clinical characteristics specific to the disease and laboratory data concerning thyroid involvement were assessed. The statistical analysis comprised general descriptive analysis and statistical tests to compare different subtypes of arthritis onset, such as juvenile Still's disease versus oligoarticular and polyarticular onset. The study was approved by the national doctoral school ethics committee.

Results: The comparative analysis in the research subgroups, according to the distribution by age, revealed approximately the same distribution of the incidence of clinical manifestations (χ2 = 10.37; DF=5; P = 0.06), differences being registered according to the distribution by sex (χ2 = 15.008; DF=5; P = 0.01). Regarding serum thyroid autoantibodies, gender differences were not revealed. Depending on the subtype of disease onset, no statistical differences were found between the research subjects. Notably, in children with systemic juvenile idiopathic arthritis (sJIA), unlike oligoarticular (oJIA) and polyarticular (pJIA) juvenile idiopathic arthritis, no cases of thyroid autoantibody positivity were observed. Based on treatment options—glucocorticosteroids (GCS) or biological disease-modifying antirheumatic drugs (bDMARDs), no statistical differences were found for antiTPO or antiTG. Anti-Tg antibodies were identified with statistical significance based on the age category at JIA onset, and strongly significant anti-Tg antibodies were observed based on disease duration as well as the patient's response to treatment.

Conclusions: The co-existence of thyroid disorder in patients with rheumatic disorders should not be underestimated. Our data suggests that sJIA is an autoinflammatory pathology, whereas other forms of JIA onset remain autoimmune rheumatologic conditions. Still, further studies will help achieve a better understanding in order to identify those children prone to developing overlap or polyautoimmune syndromes.

Key-words: Autoimmune thyroiditis, juvenile Still disease, polyautoimmune syndrom