AQP4 and sarcoidosis: It is particularly important to identify patients whose initially undifferentiated ON results from immune suppression-requiring AQP4-disease (1.2% cases), sarcoidosis (0.5% cases versus 0.03% controls, aHR 14.8, p < 0.001), Behcet’s disease (0.1% cases versus 0.01% controls, aHR 17.39, p = 0.02), and other vasculitides (besides giant cell arteritis)(0.3% cases versus 0.05% controls, aHR 4.89, p = 0.002) [8].