Juvenile idiopathic inflammatory myopathy (JDM) or Juvenile Myositis (JM) most often presents itself as Dermatomyositis (JDM) with the typical rashes and muscle weakness.  There are fewer cases of Juvenile Polymyositis (JPM), Inclusion Body Myositis (JIBM) and other clinical forms of Myositis reported.

The JDM rash precedes muscle weakness greater than 50% of the time.  In both cases, (JPM and JDM) muscle weakness usually develops over a period of days, months, or weeks.  The weakness being proximal (closest to and within the trunk of the body) primarily involves neck, hip, trunk and shoulder muscles, but may also include distal muscles.  Dysphagia (difficulty swallowing), Dysphonia (hoarseness), abdominal pain and arthritis can also occur with this disease.  Muscle pain is seen in approximately 50% of children with Myositis.

Corticosteriods are effective with complete withdrawal of medication can be anticipated in a large percentage of patients with severe weakness, who may need longer periods of treatment.  For patients who experience dose-limiting side effects of corticosteriods, or are unresponsive, there are other treatments available, including IVIg treatment.

It is important to diagnose these patients and start treatment as soon as possible.  The parents and the doctor of the child with Myositis may also consider a rehabilitation program with a team of professional experts.