Vasculitis and rheumatologic diseases may play role in the pathogenesis of acute disseminated encephalomyelitis (ADEM).

Acute disseminated encephalomyelitis (ADEM) is defined as a multifocal, monophasic, demyelinating, and inflammatory disease involving the central nervous system. It typically begins within 6 weeks of an antigenic challenge such as infection or immunization. Perivenous inflammation, edema and demyelination are the pathological hallmarks of ADEM. Reactivity of T-cells against myelin components such as myelin basic protein has been found in children with ADEM. The triggers for immune responses in ADEM are not known, but the two most widely accepted hypotheses are molecular mimicry and self-sensitization secondary to CNS infection. Inflammatory cytokines including tumor necrosis factor alpha (TNFalpha), interleukin 2 (IL2) and interferon gamma (INFgamma) are thought to be important in lesion formation in ADEM. Due to the active role of inflammatory cytokines in the pathogenesis of ADEM, any disease contributing to systemic formation of inflammatory cytokines can potentially be an etiologic factor for the initiation of ADEM. In vasculitis and rheumatologic diseases the number of T-cells, T helper type 1 cytokines and other inflammatory cytokines such as TNFalpha increase substantially. We present this hypothesis that in such setting of inflammation, adhesion molecules are up-regulated on the brain capillary endothelium by cytokines and other inflammatory mediators, altering the permeability of the brain blood barrier and so allowing for inflammatory cell migration. The migratory cells attack the basic myelin protein and the final result is the demyelination seen in ADEM. So we propose that vasculitis and rheumatologic diseases may play role in the pathogenesis of ADEM.