This process identified nine criteria that clinicians felt to be helpful or important in the diagnosis of JDM. A further process of refinement and validation is necessary to agree an internationally acceptable, clinically usable set of diagnostic criteria.

Children who develop JDM at an younger age may have increased risk of developing calcinosis. Physiologically low levels of fetuin-A in young children combined with an additional negative acute-phase effect on fetuin-A due to chronic inflammation could explain in part the propensity to develop ectopic calcification observed in JDM patients, and why calcinosis is less frequent in adults with dermatomyositis.

ObjectiveTo compare 2 groups of children with juvenile dermatomyositis (DM), those with onset of symptoms before their fifth birthday versus those whose disease begins either on or after their fifth birthday, and to assess whether age at onset is associated with differences in disease presentation, treatments received, or outcomes 2 years after diagnosis.MethodsData were analyzed on children recruited to a UK juvenile DM cohort study with a diagnosis of probable or definite juvenile DM and less than 12 months between diagnosis and recruitment.ResultsFifty-five (35%) of 157 children had onset of symptoms before their fifth birthday. At diagnosis, cutaneous ulceration was found in 32.7% of the younger group versus 11.8% of the older group (P = 0.003). Facial or body swelling was reported more often in the younger group, whereas headaches, alopecia, and Raynaud's phenomenon were all more frequently reported in the older group. At followup 2 years later, there were no important differences in outcomes between the groups. More than 90% of patients in both groups received both methotrexate and steroids. Twenty-three percent of both groups remained on steroids 2 years after diagnosis.ConclusionOur study showed that children with juvenile DM with disease onset at age <5 years are more likely to present with ulcerative skin disease and edema. There were no clinically significant differences in outcomes between the 2 groups.