Pediatric Radiologically Isolated Syndrome (RIS): A Case with Active Disease 18 Years Later

Radiologically isolated syndrome (RIS) is defined by incidental MRI findings suggestive of central nervous system (CNS) demyelination in asymptomatic individuals. While uncommon in adults, RIS is exceptionally rare in the pediatric population. Its management, particularly regarding the timing and potential benefits of high-efficacy disease-modifying therapies (DMT), remains debated. We describe a 12-year-old girl who underwent an incidental brain MRI during a school visit, revealing multiple white matter lesions. Despite being asymptomatic, the presence of cerebrospinal fluid oligoclonal bands and a high radiological lesion burden, with evidence of dissemination in space and time during follow-up, indicated a high risk of conversion to multiple sclerosis (MS). Rapid radiological worsening and marked inflammatory activity (multiple gadolinium-enhancing lesions in repeated MRI scans) despite corticosteroid treatment prompted initiation of natalizumab in 2009. Over 18 years of continuous therapy, the patient remained clinically asymptomatic, with no new MRI lesions. The patient maintained an excellent quality of life, successfully completing medical school and residency. In this case of pediatric RIS, early intervention of a high-efficacy DMT prevented clinical conversion to MS, despite aggressive radiological activity in the pre-treatment phase. The patient remained free of clinical and radiological activity over an 18-year follow-up supporting the long-term safety and sustained efficacy of natalizumab, and suggesting that proactive treatment may be beneficial in patients with high-risk RIS.