Compared with AQP4-seropositive EONMOSD, interval between (first) ON and LETM and time from first symptoms to diagnosis of NMO were longer in the late-onset group (median 13 vs. 4 months, p < 0.05; median 17 vs. 7 months, p < 0.05). The gene discussed is AQP4; the disease is neuromyelitis optica.