Multiple sclerosis under the age of ten: the challenge of a rare diagnosis in a special population - a case series.

Introduction: Multiple sclerosis (MS) is a chronic inflammatory demyelinating and degenerative disease of the central nervous system which, when it begins before the age of 18, is defined as paediatric MS. Most common clinical presentations include long tract involvement, brainstem/cerebellum syndromes, optic neuritis and acute disseminated encephalomyelitis. Paediatric-onset MS typically has a more inflammatory-active course and a higher lesion burden in imaging studies, but an extensive post-relapse recovery, with a slower long-term disability progression. The first demyelinating clinical attack occurs before 10 years old in less than 1% of patients, and, in this special population, the condition has particularities in clinical presentation, differential diagnosis, diagnostic assessment, current treatment options and outcome. Clinical cases: We present the cases of four Caucasian children (2 girls) diagnosed with relapsing-remitting MS before the age of ten, with a mean age at the time of the first relapse of 7.4 ± 2.4 years. Clinical presentation included optic neuritis, myelitis, brainstem syndrome, and acute disseminated encephalomyelitis. Baseline MRI identified several lesions, frequently large and ill-defined. Two patients were included in clinical trials and two patients remain in clinical and imaging surveillance. Conclusion: Diagnosis of MS before the age of 10 years is rare, but it has significant long-term physical and cognitive consequences, as well as a substantial impact on the current and future quality of life of the child and family. Early and correct diagnosis is essential. Prospective, randomized, large cohort studies are needed to assess the efficacy and safety of disease-modifying treatments in children under the age of ten.