Case report: The association of juvenile idiopathic arthritis (JIA) and primary demyelinating disease of central nervous system (CNS) in the same patient is rare. Here we present a 10-year-old girl formerly diagnosed with JIA who presented with acute total vision loss. Magnetic resonance imaging of the brain and spinal cord showed bilateral optic neuritis and T2 hyperintense lesions in the brain, cerebellum and cervical spinal cord, some of them gadolinium-enhancing. Oligoclonal bands were present in the cerebrospinal fluid. Visual evoked potentials were prolonged. Aquaporin-4 antibodies were negative. The patient was treated with methylprednisolone 30 mg/kg daily for five days, resulting in improvement in vision and gait. This first demyelinating event in this patient with JIA with clinical and paraclinical features meeting the 2017 MS diagnostic criteria supports a possible predisposition to autoimmune disorders.