JDM can present with a specific pattern of muscle weakness (involvement of muscles in the thighs and upper arms) and specific skin rashes: in these cases JDM is easier to diagnose. Each child is different and your doctor will decide on the best tests for each child. Sometimes JDM can look like other autoimmune disease or like a congenital muscle disease. The tests will help work out which disease your child has.
On physical examination, your doctor will check muscle strength, skin rashes and the blood vessels in the nail beds.