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ObjectiveJuvenile idiopathic arthritis JIA is a heterogeneous disease involving chronic arthritis. The clinical course is characterized by a fluctuating pattern of active and inactive disease. We have described in detail the clinical course in different JIA subtypes during the first 2 years after diagnosis and studied its relationship to disease activity in the following years.MethodsDetailed clinical data on different parameters describing the disease activity in sequential time periods covering the first 2 years after diagnosis were retrieved from the charts of 311 patients with JIA and compared between subtypes. In a cohort of 146 patients, the relation of these different clinical variables to the course of disease in the following 3 years was evaluated.ResultsThe percentage of time with active disease in the first 2 years differed significantly between subtypes. In all subtypes, a broad spectrum of activity was observed. The time with active disease in the first 2 years was the most significant factor associated with the duration of active disease in the following years.ConclusionDifferent percentages of time with active disease have been observed between JIA subtypes in the first 2 years. The cumulative duration of activity varied widely within each subtype. Regarding the prognosis of the individual patient, the clinical course in the first 2 years appears to be predictive of the clinical course in the following years. Patients that have less time with active disease in the first 2 years are not likely to develop an unremitting clinical course later on.

ObjectiveMethotrexate MTX is the most commonly used diseasemodifying antirheumatic drug in juvenile idiopathic arthritis JIA. Currently, individual response to MTX cannot be reliably predicted. Identification of clinical and genetic factors that influence the response to MTX could be helpful in realizing the optimal treatment for individual patients.MethodsA cohort of 128 JIA patients treated with MTX were studied retrospectively. Eleven clinical parameters and genotypes of 6 single nucleotide polymorphisms in 5 genes related to the mechanism of action of MTX were compared between MTX responders and nonresponders using a multivariate regression analysis.ResultsThe time from diagnosis to start of MTX treatment, physicians global assessment at baseline, and the starting dose were significantly associated with the response to MTX at 6 months after initiation. Patients with a shorter time from diagnosis to start of MTX and a higher disease activity according to the physician but with a lower MTX dose showed an increased response. The effect of the starting dose on MTX response seemed to be mainly due to the influence of the systemic JIA subtype. The time from diagnosis to start of MTX treatment and physicians global assessment at baseline were highly correlated. Therefore, the precise effect size of each independent variable could not be determined.ConclusionIn children with JIA, the time from diagnosis to start of MTX appears to be an important factor for MTX response. Our results suggest that an earlier start of MTX treatment will lead to an increased response.

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