Abstract We present a rare case of simultaneous muscle weakness and cutaneous depigmentation. Muscle and skin biopsies confirmed the diagnosis of polymyositis and generalized vitiligo vulgaris. All symptoms improved after steroid therapy. Immunohistochemical analyses revealed predominant CD8-positive T cell infiltration in both muscular and cutaneous lesions. This case suggests that a common autoimmune mechanism mediated by cytotoxic T lymphocytes underlies the pathogeneses of these two diseases.