To develop a composite DAS for JDM and provide preliminary evidence of its validity. The Juvenile DermatoMyositis Activity Index (JDMAI) is composed of four items: physician's global assessment of overall disease activity; parent's/child's global assessment of child's wellbeing; measurement of muscle strength; and assessment of skin disease activity. The score of the JDMAI is the arithmetic sum of the scores of each individual component. Six versions of the JDMAI were tested, which differed in the tools used to assess the third and fourth items. Validation procedures were conducted using three large multinational patient samples including a total of 627 patients. The JDMAI was found to possess face and content validity, good construct validity, satisfactory internal consistency (Cronbach's alpha = 0.58-0.89), fair responsiveness to clinically important change (standardized response mean = 0.82-3.12 among patients improved) and strong capacity to discriminate patients judged as being in the state of inactive disease or low, moderate or high disease activity by the physician (P < 0.001) or whose parents were satisfied or not satisfied with the course of their child's illness (P < 0.001). Overall, the six versions of the JDMAI showed similar metrological performances in validation analyses. The JDMAI was found to possess good measurement properties in a large population of patients with a wide range of disease activity, and is, therefore, suitable for use in both clinical and research settings. The final version of the JDMAI will be selected after its prospective validation.

The search for biomarkers in juvenile idiopathic arthritis (JIA) is a promising and rapidly expanding field of investigation. The biomarkers identified so far may help to dissect the clinical heterogeneity of the illness, measure the level of disease activity, predict clinical remission, relapse, response to medications, course over time, complications, and forestall disease flares. We provide a summary of the most recent advances in the development and application of biomarkers in JIA. We performed a PubMed search for significant articles combining predetermined keywords related to biomarkers in non-systemic and systemic JIA, chronic uveitis, and macrophage activation syndrome (MAS).The biomarkers available or under study are presented and discussed separately for non-systemic and systemic subtypes and for the two main disease complications, uveitis and MAS. The incorporation of valid and reliable biomarkers in standard clinical care may help to design better patient-tailored treatment regimens and to improve the therapeutic strategies based on the treat-to-target approach. The establishment of biomarkers that predict the risk of disease flare may lead to define the optimal modalities for treatment discontinuation after the achievement of clinical remission.

Juvenile psoriatic arthritis (JPsA) accounts for 1–7% of all cases of juvenile idiopathic arthritis (JIA) and its definition has been a matter of controversy among pediatric rheumatologists for many years. The traditional attribution of JPsA to the spondyloarthropathy group was challenged in the early 1990s, whereas the recent demonstrations of its heterogenous nature have led to questions about its identification as a distinct category in JIA classification. It has been shown that children with the phenotype of JPsA can be divided in two subgroups, one presenting with the features of early-onset ANA-positive JIA, and another that belongs to the spectrum of spondyloarthropathies. The few studies that have compared the clinical characteristics and genetic determinants of JPsA with those of the other JIA categories have obtained contrasting findings. The debate on the categorization of JPsA as a distinct entity within JIA classification is still ongoing and has prompted the revision of its current classification.