A prospective population based study on outcome of juvenile chronic arthritis in Costa Rica

To study the disease process and outcome in an unselected group of patients with juvenile chronic arthritis (JCA).

From a population based study in San José, Costa Rica, 47 patients with JCA with disease onset from 1993 through 1995 were investigated after median duration of 4.1 yrs (range 2.9-4.9) (incidence group). Another 49 children with disease onset prior to 1993 and younger than 16 years of age on December 31, 1995 (cross sectional group) were also followed.

In the incidence group, 4/47 children changed subtype during the course of the disease. All did so within 2 years from disease onset, and the same observation was made in the cross sectional group. Uveitis was described at onset in a single case, and no child developed uveitis later. In patients from the incidence group in the process of being transferred to adult rheumatology clinics, 48% were still taking medication. Patients who had involvement of proximal interphalangeal (PIP) joints at onset had an increased risk of being active or stable at followup (RR 12.3, 95% CI 1.4-108.3). A higher chance of no continuing disease activity at followup was observed in children with oligoarticular disease than in the other subtypes (RR 2.8, 95% CI 1.2-6.9).

Uveitis associated with antinuclear antibody positive JCA and psoriatic arthritis in Costa Rican children is uncommon, and the risk of developing uveitis remains low during the course of the disease. Involvement of PIP joints predicts an increased risk of continuing disease. The course of JCA in Costa Rican children is not milder than in Caucasian populations, since 48% of the patients showed persistent disease activity at the transition to adult care.