Granulomatosis with polyangiitis (GPA), Wegener's Granulomatosis (WG), is a systemic inflammatory disease of unknown etiology, with small and medium arteries involvement, characterized by necrotizing granulomatosis. In this article, we present a patient who was referred to our Multiple Sclerosis ( MS) outpatient clinic due to the results of MRI scans suspicion of MS, however was diagnosed as GPA with the peripheral and central nervous systems involvement as a result of the examination. 39-year-old female had visual impairment, hearing loss, and weakness in her right arm and leg. In her history, she had shortness of breath and complaints of painful urination and bloody urine. Her visual acutiy was both 0.4. In the muscle strength examination, right upper extremity was 3/5 and right lower extremity was 2/5. There was hypoesthesia in the right extremity. Biochemistry values were normal. She had diffuse purpuritic lesions of the lower extremity. On cranial MRI, in non-specific T2-FLAIR hyperintense foci settled in white matter and the right optic nerve was evaluated to have a slight kink. Multiple Sclerosis (MS) is an autoimmune central nervous system (CNS) disease characterized with inflammation, demyelination and axon damage. MS is diagnosed according to McDonald’s Criteria that revised in 2017. A lot of disase-disease- are in the differential diagnosis of MS. GPA may affect peripheral and central nervous systems in varying proportions (10%-45%). Although GPA is with atypical onset especially involvement of central nervous system is rarely seen, it takes part in the differential diagnosis of MS. Keywords: A Rare Disease, Differential Diagnosis of Multiple Sclerosis, Granulomatosis with Polyangiitis, Rheumatological Diseases with Atypical Course