Neuromyelitis optica--complication or comorbidity in primary Sjögren's syndrome?

We report two cases of neuromyelitis optica (NMO) associated with primary Sjögren's syndrome (pSS), comparing the clinical and laboratory features of these predominant neurological patients and reporting their different outcome. NMO - a severe demyelinating disorder of the central nervous system - primarily affects the spinal cord and optic nerves, resulting in longitudinally extensive transverse myelitis and/or optic neuritis. Our patients had a late pSS diagnosis, due to the absence of sicca syndrome and specific Sjögren serology in the early stages of their diseases, when the neurological symptoms prevailed. Many NMO patients have an accompanying autoimmune disease, most commonly Sjögren syndrome and systemic lupus erythematosus or a related profile of non-organ-specific autoantibodies. Neurologic involvement occurs in approximately 20% of patients with pSS, usually preceding the diagnosis (in 75-80% of the cases) [1,2]. The frequency of both neurologic manifestations (revealing pSS) and negative autoimmune serology, especially in the event of CNS involvement, could explain why underlying pSS is misdiagnosed [3,4]. Screening for pSS should be systematically performed in cases of acute or chronic myelopathy and/or cranial nerve involvement, mainly because these patients have a severe outcome. The presence of the anti-aquaporin4 antibodies, besides anti-Ro and anti-La, in both reported cases, is intriguing and raises the question of whether we are facing two distinct diseases or the NMO is just complicating an unusually less expressive Sjögren's syndrome subtype.