[A 25-year-old woman with primary Sjögren syndrome who developed optic neuritis and encephalomyelitis associated with an anti-aquaporin 4 antibody].

We report a 25-year-old woman who developed optic neuritis and encephalomyelitis following primary Sjögren's syndrome (SjS). SjS began with Sicca syndrome when she was 8 years old, and neurological involvement subsequently developed at the age of 10 with right hemiparesis. Based on clinical symptoms, serum positive for SS-A and SS-B antibodies and pathological findings of the salivary gland, we confirmed a diagnosis of primary SjS. Magnetic resonance imaging (MRI) revealed multiple lesions in the brain and the spinal cord. These led diagnosis of SjS with central nervous system involvement (CNS-SjS) and initiated steroid therapy. At the age of 25, the patient developed left visual loss due to retrobulbar optic neuritis, left lower quadrantic hemianopia, numbness of the right upper limb, and weakness of both legs. Laboratory examinations showed that her serum was positive for SS-A and SS-B antibodies, and her cerebrospinal fluid had elevated levels of total protein and myelin basic protein without pleocytosis. Her brain MRI revealed multiple T2-high-intensity lesions bilaterally in the frontal subcortical white matter and in the right temporo-parietal subcortical white matter. The lesions included a tumefactive lesion and an active lesion. Additionally, the spinal MRI revealed a severely atrophied spinal cord with T2-high-intensity lesions extending longitudinally and centromedullary in the spinal cord. These findings led us to examine the patient's serum for anti-aquaporin (AQP) 4 antibodies and the test confirmed that her serum was positive for the antibodies. After administering intravenous high-dose methylprednisolone (1,000 mg/day for 3 days), her symptoms markedly improved with normalization of myelin basic protein. However, her serum remained positive for AQP 4 antibodies. We think that the patient's diagnosis belongs to the neuromyelitis optica (NMO) spectrum disorders associated with autoimmune disorders. This is a rare case in that the initial presentation was SjS and occurred at a very young age.