Juvenile dermatomyositis (JDM), the form of JIIM with characteristic photosensitive skin rashes, including Gottron’s papules and heliotrope rash, is the most common of the JIIM and is thought to be mediated by CD4+ T cells, B cell and dendritic cell attack on muscle capillaries, whereas juvenile polymyositis (JPM), the form of JIIM without characteristic rashes, is thought to be mediated by CD8+ T cells on myofibers [15–17]. The gene discussed is CD4; the disease is juvenile polymyositis.