Acute disseminated encephalomyelitis (ADEM)
MOG-IgG serum antibodies were first identified in a subset of children with ADEM (28,29). Children with ADEM represent the most common phenotype among all MOGAD patients and account for almost 50% of paediatric MOGAD patients (2,24). Clinical presentation of ADEM includes polyfocal neurological deficits and encephalopathy (i.e. behavioural changes or altered consciousness), not explainable by fever (30). It has recently been shown that up to 50% of all children with ADEM are seropositive for MOG-IgG (31). In these patients, MOG-IgG seroprevalence is associated with a higher risk for longitudinally extensive transverse myelitis (LETM), but with resolution of brain lesions and a better outcome compared to MOG-IgG negative ADEM patients (32). Relapses can occur with further episode(s) of ADEM as multiphasic ADEM (MDEM), with ON (ADEM-ON), or transverse myelitis (ADEM-TM) (33). Notably, persistent seroprevalence of MOG-IgG is strongly associated with an increased risk for relapsing disease (34,35).