Here, we summarize the current evidence examining the role of CD8+ T cells in systemic lupus erythematous (SLE), systemic sclerosis (SSc), Sjögren’s syndrome (SS), polymyositis (PM) and dermatomyositis (DM) with special focus on commonalties in adult and juvenile connective tissue diseases (CTDs) in CD8+ T cell peripheral blood phenotypes, CD8+ T cell function, and organ-specific CD8+ T cell profiles. The gene discussed is CD8A; the disease is polymyositis.