We report the case of a 31-year-old woman who presented with neuromyelitis optica (NMO) associated with Sjögren syndrome and distal renal tubular acidosis. She was hospitalized because of cervical transverse myelopathy and right optic neuritis. She had been clinically diagnosed with Sj6gren syndrome, with a high titer of anti-SS-A antibody (1:500) and anti-SS-B antibody (1:498). She also showed hypokalemia, metabolic acidosis, and nephrocalcinosis caused by distal renal tubular acidosis associated with Sjögren syndrome. T2-weighted magnetic resonance imaging (MRI) revealed long lesions extending from the medulla oblongata to the lower thoracic cord. In addition, gadolinium-enhanced MRI revealed a right optic nerve lesion in the optic canal. High titer of anti-aquaporin-4 (AQP4) antibody was detected in the patient's serum (1:131,072). A combination therapy comprising steroid pulse therapy and plasmapheresis improved her clinical symptoms, and the administration of oral prednisolone (20 mg/ day) was effective in preventing the recurrence of NMO. In patients with myelitis/transverse myelopathy associated with autoimmune disorders such as Sjögren syndrome, examining the titer values of anti-AQP4 antibody is indispensable in determining the appropriate therapy.