The investigation and management of which has slowly evolved over the last two decades, necessitating a rethink of diagnostic criteria. The Children’s Arthritis and Rheumatology Research Alliance (CARRA) and the United Kingdom Juvenile DM Cohort are leading
data generators in this field, supplemented in this issue of the Journal see more by two smaller cohorts of JDM from the diverse APLAR region.[1, 2] Prasad et al. from India and Gowdie et al. from Australia report a prevalence of muscle weakness, Gottron’s papules, and heliotrope rash not so greatly different from the initial 1975 descriptions by Bohan and Peter,[3, 4] and very similar to the 2011 description of European and Latin American patients with JDM, in spite of different time period and sociocultural diversities. This two cohorts provide useful insights into the diverse clinical manifestations over and above those currently used for diagnostic classification, and both emphasise dysphagia and dysphonia. Disease manifestations may change between early and late childhood, with the UK JDM cohort reporting that children with disease onset before age 5 years were more likely to present with oedema and ulcerative skin disease.
Navitoclax mouse Gowdie et al. found nail fold changes in 68% of their cohort unlike the finding of reduced nailfold capillary density virtually in all JDM patients in a longitudinal study by Schmeling et al. Although capillaroscopic change seems to be a marker of both skin and muscle disease activity, and has been suggested as a diagnostic criterion, it requires
further refinement and precision to become a clinically useful tool in JDM. The dreadful complication of calcinosis cutis occurs in 20% to 40% of cases and more so with increasing disease duration.[10, 11] Delayed or inadequate therapy and persistent skin inflammation are thought to be predisposing factors. None of the children in the Australian series  had calcinosis at diagnosis, though 18% had developed this probably in the PAK6 more chronic phase. The Indian series had 27% of their children with calcinosis at presentation or during follow up, which has been reported by other Indian studies, and is higher than reports from other countries  possibly due to a delayed diagnosis and initiation of treatment, thereby a higher cumulative period of active disease and accrual of damage. Indeed, the median duration of symptoms prior to diagnosis in the Indian study was 9.25 months  as compared to 2.8 months in the Australian report  and 5 months in the cohort of 384 children of United states pooled from 55 paediatric rheumatology clinics. The factors influencing the variation in time to diagnosis and initiation of therapy which favourably impacts on both mortality and morbidity warrant further study.