Objective: To evaluate the difference between adult juvenile idiopathic arthritis (JIA, starting at <16 years) and rheumatoid arthritis (RA).Methods: Data on 128 adult JIA patients were from the National Database of Rheumatic Diseases in Japan (NinJa), 2014, divided into 4 groups by period of disease onset (Group 1: 2000-2013, n = 32; Group 2: 1981-1999, n = 32; Group 3: 1966-1980, n = 31; Group 4: ∼1965, n = 33). Disease activity, treatment and long-term prognosis of adult JIA patients were compared with RA patients matched for sex- and disease duration in each era.Results: In Groups 1 and 2, adult JIA patients had significantly lower clinical disease activity indices (CDAI) (Group 1: adult JIA 1.5 [0.4-6.9]-vs-RA 5.3 [2.5-10.3], p = .001, Group 2: 2.6 [0.6-9.0]-vs-6.9 [3.5-11.0], p = .001, shown as median [quartile range], p-value, respectively), and had higher CDAI remission rates than RA patients (Group 1: 54.8%-vs-28.2%, p = .002, Group 2: 51.7%-vs-17.0%, p < .001). More adult JIA than RA patients in Group 1 used biologics (62.5%-vs-24.7%, p < .001). However, there were no adult JIA-vs-RA differences in joint destruction and physical function in any group.Conclusions: Adult rheumatologists must recognize that adult JIA patients are different from RA patients even when disease duration is the same.
Keywords: Transition; adult Juvenile idiopathic arthritis (JIA); rheumatoid arthritis (RA).