Background/Purpose: There is no consensus in the literature with regard to the features and long-term prognosis of psoriatic arthritis (PsA) starting in childhood (jPsA). We aimed to describe the outcome of patients with jPsA in comparison to adult-onset (aPsA).

Methods: A large cohort of PsA patients  with known diagnosis date and follow-up were divided into two groups according to the age at PsA diagnosis: jPsA- diagnosis ≤16 years of age and aPsA >16 years of age.  The two groups were compared regarding demographics, family history, disease manifestations (number of tender (TJ) and swollen (SJ) joints, enthesitis, dactylitis, the presence of inflammatory back pain, skin involvement (PASI score), comorbidities, functional class (FC), patient and physician assessments of diseases activity at baseline and after 5, 10, 15, 20, and 25 years of follow-up. Patients’ contribution to the time interval follow-up groups depended on their follow-up period in the database.  Adjusted mean scores were calculated for all disease manifestations during each follow-up period. Chi square test, Student’s t-test or Mann-Whitney test were used, as appropriate to compare between the two groups.  Comparisons of comorbidities between the two age groups included first time diagnosis during follow up, cumulative morbidity and the influence of disease duration. Generalized estimating equations procedure of repeated measurements were performed to assess the effect of age on study variables. Relative risk ratios and 95% confidence intervals were calculated from the models. The results were considered statistically significant for 2-sided p value< 0.05.

Results: The jPsA group included 78 patients, 41% males, age at diagnosis 11.48±4.97 years, age at baseline 33.53±14.92 years, contributing 612 patient visits. The aPsA group consisted of 2182 patients, 54.2% males (p=0.02), age at diagnosis 40.29±13.15 years, age at baseline 47.47±13.28 years, contributing 19784 patient visits. Arthritis preceded psoriasis in 21(26.9%) individuals  in the jPSA group compare to 123 (5.6%) in the aPsA group (p< 0.0001).  After ≥25 years of disease, the following adjusted mean scores were reported in the jPsA group:  TJ= 3.86±6.04, SJ= 1.18±3.05, enthesitis 0.21±0.64, dactylitis 0.2±1.22, inflammatory back pain in 20.8%. The majority (62.5%) were in FC I, 32.5% in FC II, and 5% in FC III.  No statistically significant differences were noted between jPsA and aPsA groups in TJ, SJ, enthesitis and dactylitis counts, PASI score, inflammatory back pain, or FC nor in   the patient and physician assessments of disease activity. There were no statistically significant differences in the prevalence of malignancy, hyperlipidemia, diabetes mellitus and myocardial infarction between the two groups although the jPsA group was much younger.  Hypertension was more common in the aPsA (47.2% versus 20.6%, p=0.003) whereas depression was more common in the jPsA group (20.6% versus 8.7%, p=0.03).

Conclusion: The overall prognosis of jPsA ≥25 years following diagnosis is good and resembles that of aPsA group. However, patients with jPsA developed  joint symptoms earlier compared to skin disease, and accrue comorbidities at a younger age.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/long-term-outcome-of-juvenile-onset-psoriatic-arthritis/