AQP4 and neuromyelitis optica: Of the 20 patients with labial gland biopsy, 16 were positive, while only 4 patients had elevated anti-SSA antibodiy, emphasizing the important role of labial gland biopsy in early diagnosis of SS. Subsequently, identified 8 patients were identified with spinal cord involvement from 112 patients with SS referred to the neurology department, and 7 of them met the diagnostic criteria for NMO and with positive AQP4-IgG