Clinical characteristics of juvenile idiopathic arthritis in an area of central Italy: a population-based study

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in children and an important cause of short and long-term disability. In a recent systematic review of population based studies, the epidemiology of JIA is variable worldwide with incidence rates ranging between 1.6 and 23.0/100,000, and prevalence rates between 3.8 and 400.0/100,000. We investigate the incidence and describe the characteristics of juvenile idiopathic arthritis in the pediatric population of the central Italy, in the period 2000-2009.

A retrospective study was conducted in the Marche region to identify patients with a diagnosis of juvenile idiopathic arthritis according to ILAR criteria, between January 1, 2000 and December 31, 2009. JIA was classified according to the ILAR criteria, that is, arthritis of unknown etiology that persisted for > 6 weeks with onset before the age of 16 years. The pooled global ascertainment of cases was estimated by capture-recapture methods and two independent information sources of ascertainment of new cases of JIA were considered.

We studied 151 patients (56 males, 37.1% and 95 females, 62.9%) meeting the ILAR criteria of juvenile idiopathic arthritis. Mean age at presentation was 6.8 ± 3.7 years for males and 6.0 ± 4.0 years for females (p=0.22). The overall incidence rate was 6.34 per 100,000/year (C.I. 6.26-7.35) and the total incidence rate increase from 2000-2009 was 8.16%. Oligoarthritis was the most common onset type (n=98, 65.0%) with 62.5% of ANA-positive patients in at least two determinations.

Our results indicate that juvenile idiopathic arthritis incidence rates in Italy are comparable to previous data from southern Europe, with a higher frequency of oligoarthritis. To the best of our knowledge, this is the first population-based epidemiological study carried out in Italy focusing on the incidence of juvenile idiopathic arthritis.