Juvenile dermatomyositis is very rare.
We think that it may arise in children who have a particular genetic predisposition which may cause problems in clearing certain viruses from the system. However, it is not contagious or catching, and it does not affect other family members. Fortunately, in most children treatment results in rapid improvement, although it will need to be continued for some time and monitored carefully to ensure the optimum response. It is important to stress that the childhood form of dermatomyositis differs from adult polymyositis in which inflammation of muscle, usually without any other organ involvement, is caused by infiltration of muscle by cells called lymphocytes. It differs also from the adult form of dermatomyositis which occurs in older people and may be associated with an underlying tumour.