Cutaneous polyarteritis nodosa presents with typical cutaneous lesions of polyarteritis nodosa without visceral involvement at the time of diagnosis. We report a 32-year-old woman with a 12-year history of myasthenia gravis under immunosuppressive treatment, who presented with tender, erythematous nodules 20 mm in diameter on her shins. A diagnosis of cutaneous polyarteritis nodosa was made, based on the clinical and histopathological findings. Myasthenia gravis, an antibody-mediated disease, is occasionally accompanied by other autoimmune diseases, but we found no previous report in the literature associating it with polyarteritis nodosa.