Do the features of juvenile psoriatic arthritis change according to age? A comprehensive evaluation of the PeRA Research Group Registry.

OBJECTIVES: To describe the clinical features and treatment outcomes of children with juvenile psoriatic arthritis (JPsA) and to compare the distinct patterns of the disease between early-onset and late-onset age groups.

METHODS: Patients with JPsA followed regularly for at least 6 months between 2010-2020 in 7 pediatric rheumatology centers in Turkey were included in the study. The demographic features, clinical manifestations, treatment strategies, and outcomes of the patients were evaluated retrospectively.

RESULTS: Eighty-seven (46 male/41 female) patients were included in the study. The mean age at diagnosis was 11.9 ± 4.5. Fifty-seven (65.5%) patients had psoriasis at the time of diagnosis, arthritis preceded psoriasis in 10 (11.5%) patients. Thirty (34.5%) patients had dactylitis, 28 (32.2%) had nail pitting, 36 (41.4%) had involvement of the small joints, 20 (23%) had enthesitis. Sacroiliitis was detected in 11 (12.6%) patients by magnetic resonance imaging. Anti-nuclear antibodies (ANA) were positive in 35 (40.2%) patients. Twelve children (%13.8) were in the early-onset (<5 years) group. Uveitis and ANA positivity were more common in the early-onset group. Active joint counts and activity scores of our patients showed significant improvement at 6th month and at the last control compared with baseline.

CONCLUSION: About one-third of patients with JPsA do not have psoriasis at the time of diagnosis. In some patients, no skin lesion is seen during the course of the disease. Children with psoriatic arthritis seem to display two different phenotypes. Younger children have female predominance, ANA positivity, and uveitis, while older children have more axial involvement.