Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory disorder of the CNS characterized by a widespread demyelination that predominantly involves the white matter of the brain and spinal cord. The condition is usually precipitated by a viral infection or vaccination. The presenting features include an acute encephalopathy with multifocal neurologic signs and deficits. Children are preferentially affected. In the absence of specific biologic markers, the diagnosis of ADEM is still based on the clinical and radiologic features. Although ADEM usually has a monophasic course, recurrent or multiphasic forms have been reported, raising diagnostic difficulties in distinguishing these cases from multiple sclerosis (MS). The International Pediatric MS Study Group proposes uniform definitions for ADEM and its variants. We discuss some of the difficulties in the interpretation of available literature due to the different terms and definitions used. In addition, this review summarizes current knowledge of the main aspects of ADEM, including its clinical and radiologic diagnostic features, epidemiology, pathogenesis, and outcome. An overview of ADEM treatment in children is provided. Finally, the controversies surrounding pediatric MS and ADEM are addressed.

Aquaporin-4 autoimmunity is a distinctive recurrent and widespread inflammatory CNS disease in children.

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Multiple sclerosis (MS) typically manifests in early to mid adulthood, but there is increasing recognition of pediatric-onset MS, aided by improvements in imaging techniques. The immunological mechanisms of disease are largely unexplored in pediatric-onset MS, in part because studies have historically focused on adult-onset disease. We investigated autoantibodies to myelin surface Ags in a large cohort of pediatric MS cases by flow cytometric labeling of transfectants that expressed different myelin proteins. Although Abs to native myelin oligodendrocyte glycoprotein (MOG) were uncommon among adult-onset patients, a subset of pediatric patients had serum Abs that brightly labeled the MOG transfectant. Abs to two other myelin surface Ags were largely absent. Affinity purification of MOG Abs as well as competition of binding with soluble MOG documented their binding specificity. Such affinity purified Abs labeled myelin and glial cells in human CNS white matter as well as myelinated axons in gray matter. The prevalence of such autoantibodies was highest among patients with a very early onset of MS: 38.7% of patients less than 10 years of age at disease onset had MOG Abs, compared with 14.7% of patients in the 10- to 18-year age group. B cell autoimmunity to this myelin surface Ag is therefore most common in patients with a very early onset of MS.

We provide evidence supporting independent and causal effects of decreased vitamin D levels and increased BMI on susceptibility to pediatric-onset MS.