Update on the Incidence of Paediatric Multiple Sclerosis, Myelin Oligodendrocyte Glycoprotein Antibody–Associated Disease, Aquaporin-4 Antibody–Positive Neuromyelitis Optica Spectrum Disorder, and Other Acquired Demyelinating Syndromes in the Netherlands, 2017–2025, Including the COVID-19 Pandemic

Background: Acquired demyelinating syndromes (ADS) in children include multiple sclerosis (MS), myelin oligodendrocyte glycoprotein antibody–associated disease (MOGAD), aquaporin 4 antibody-positive neuromyelitis optica spectrum disorder (AQP4+ NMOSD), and other seronegative disorders. We previously reported an increased incidence of overall paediatric ADS and MS between 2007 to 2010 and 2011–2016 (from 0.66 to 0.80 and 0.15 to 0.26 per 100,000 person-years, respectively). Environmental factors, including viral exposure, may influence these rates. Comparing a recent period that includes the COVID-19 pandemic provides an opportunity to study temporal patterns. Methods: Children < 18 years with a first demyelinating event between January 2017 and June 2025 were prospectively included in the nationwide PROUDkids 2.0 study or referred to the Dutch Paediatric MS Centre. Diagnoses followed international criteria, and incidence rates were calculated using national population data. Results: Among 257 included children, 111 (43%) had MS, 93 (36%) MOGAD, 5 (2%) AQP4+ NMOSD, and 48 (19%) seronegative ADS. Overall ADS incidence was 0.91 per 100,000 person-years, with MS 0.40, MOGAD 0.33, AQP4+ NMOSD 0.02, and seronegative ADS 0.16 per 100,000 person-years. Compared with 2011–2016 (0.26 per 100,000), MS incidence increased, whereas other ADS rates remained stable. MS incidence declined after COVID-19 restrictions, particularly among adolescents, while MOGAD incidence rose modestly in younger children during the COVID restrictions. Conclusions: Paediatric MS incidence continues to rise in the Netherlands, whereas the incidence of other ADS remains stable. Temporal variations in the incidence of MS and MOGAD during and after the COVID-19 pandemic may reflect the influence of viral exposure in their pathogenesis.