Approach to evaluation of suspected idiopathic inflammatory myopathy (IIM) in children

The typical presentation for IIM in children is symmetric (eg, both legs, both arms, and/or neck flexors on both sides) proximal muscle weakness that gradually worsens over months in a child 5 to 10 years of age. The weakness may also be present distally but to a lesser degree. The child may have functional limitations due to the proximal muscle weakness. Most commonly, patients have both proximal muscle weakness and characteristic skin rashes. However, some patients may only have weakness, whereas other may only have the rashes. Characteristic skin rashes include heliotrope rash (reddish-purple rash on the upper eyelids with periorbital edema), Gottron papules (erythematous, papulosquamous eruption over the dorsal surfaces of the knuckles), or Gottron sign (flat, erythematous rash over the dorsal surfaces of the knuckles).