This case report concerns the diagnosis of two independent chronic diseases in a patient hospitalized for stroke, myasthenia gravis (MG) and giant cell arteritis (GCA). MG has been found to be associated with several diseases, but there are very few cases documenting its coexistence with GCA. We report the case of a 79-year-old woman initially hospitalized for stroke. Patient's concurrent symptoms of blepharoptosis, dysphagia, and proximal muscle weakness were strongly suggestive of myasthenia gravis. The persistent low-grade fever and elevated inflammatory markers in combination with the visual deterioration that developed also raised the suspicion of GCA. Histological examination confirmed GCA, while muscle acetylcholine receptor antibodies were also present. Even though in medicine one strives to interpret a patient's symptoms with one diagnosis, when one entity cannot fully interpret the clinical and laboratory findings, clinicians must consider the possibility of a second coexisting illness.