Usually no treatment is necessary. Spontaneous remission occurs in
Every year between and people per million receive a diagnosis of PM or DM.  Around children per million per year are diagnosed with DM (termed juvenile dermatomyositis ), with an average age of onset of seven years. Diagnosis of adult DM commonly occurs between 30 and 50 years of age. PM is an adult disease, usually emerging after the age of twenty. PM and DM are more common in females, more common in Caucasians, and least common in Asians. At any given time, about people per million have IBM; it emerges after the age of 30 (usually after 50), and may be more common in males. 
The main aim of lupus treatment is to manage acute periods of potentially life threatening ill health, minimize the risk of flares during periods of relative stability and controlling the less life-threatening, but often incapacitating day to day symptoms (1).