P 855. Epidemiology of Neuromyelitis Optica Spectrum Disorders in Children and Adolescents

Background: Neuromyelitis optica spectrum disorders (NMOSDs) are severe autoimmune disorders of the central nervous system (CNS) characterized by recurrent episodes of uni- or bilateral optic neuritis (ON), transverse myelitis (TM), and brain stem syndromes (BS). A majority of adult patients have serum autoantibodies against aquaporin-4 (AQP4-ab), directed against the water channel aquaporin-4. In pediatric patients, AQP4-ab is less frequently detectable than autoantibodies against myelin oligodendrocyte glycoprotein (MOG-ab). Until recently, patients with MOG-ab were thought to have a better prognosis and a milder disease course than patients with AQP4-ab. However, recent studies could show that pediatric and adult NMOSD patients with MOG-ab may also have recurrent disease courses.

One-third of group of children with NMOSD consists of patients without AQP4- or MOG-ab. Clinically, they commonly present with simultaneous or sequential episodes of ON and longitudinally extensive TM (LETM).

Objectives: Evaluation of epidemiological data regarding incidence and prevalence of pediatric NMOSD in German speaking countries. Furthermore, differences between the three above-mentioned groups in terms of radiological characteristics, cerebrospinal fluid (CSF) profile, therapy response, and long-term outcome need to be assessed. Therefore, studies with adequate patient numbers are needed to evaluate the epidemiology, long-term outcome, and prognosis of pediatric patients with NMOSD, either with AQP4-, MOG- or without antibodies.

Methods: Already begun initiatives to assess pediatric NMOSD patients (ESPED, ESNEK, BIOMARKER study, und NEMOS junior) are continued. We receive data regarding clinical symptoms, therapy regimen, and therapy response via a standardized questionnaire. These clinical data are evaluated together with the CSF profile (cell count, cytology, protein, immunoglobulins, and serology), autoantibody status (AQP4-ab, MOG-ab, new autoantibodies) and the cerebral and spinal imaging methods.

Results: Since 2009, more than 600 children with a demyelinating event (among them 14 NMOSD patients; 7 MOG-ab, 5 AQP4-ab positive, and 2 seronegative) and between March 3, 2017, and March 31, 2018, via ESPED from Germany overall 13 children and adolescents (seven females and 6 males) were referred with newly diagnosed NMOSD. Despite inclusion criteria following Wingerchuk 2015, 8/13 referred children and adolescents did not fulfill these criteria. The reason to follow these eight patients (2/8 MOG-ab positive), nevertheless, is their risk of experiencing another episode and thus fulfilling diagnostic criteria for NMOSD. In one/eight patients, the autoantibody status was still lacking. From the five definite NMOSD patients, two showed AQP4-ab, two MOG-ab, and one none. Three/five were male, median age was 11 years. One patient with AQP4-ab and the seronegative patient had a first event with bilateral ON und LETM, and the other patient with AQP4-ab had a BS. Both patients with MOG-ab presented with simultaneous ON and LETM. Acute therapy was an intravenous methylprednisolone pulse in five/five patients. The first patient with AQP4-ab did not get a long-term therapy, and the second one got rituximab.

Conclusion: Considering 11 million children under 14 years of life in Germany, the incidence for NMOSD is 0.5 per 100,000 children. This resembles already published data. However, it is unlikely that all newly diagnosed children were referred to our study, thus, the true incidence is indeed higher.