Paediatric MOGAD encephalitis can result in poor long term outcome (mRS>2) with progression to leukodystrophy or cortical atrophy. 2 Indeed, MOG antibody accounts for the majority of ADEM and non-ADEM autoimmune encephalitis (AE) presentations in children 8,10 and is associated with a higher risk of relapse than MOG antibody negative disease. 7Īcute disseminated encephalomyelitis (ADEM) is the most common initial presentation in children under 9 years. 8,9 Residual paraparesis is less common than in AQP4-NMOSD. Early bowel, bladder and sexual dysfunction, reflecting central cord and conus involvement, increases suspicion for MOGAD. Both longitudinally extensive and short segment TM are observed. 2 TM in MOGAD may mimic that seen in AQP4-NMOSD and MS. It is the second most frequent presentation in adults and older children. Transverse myelitis (TM) may occur in isolation or with ON to mimic Devic’s disease. 6,8 Symptom resolution is anticipated but up to 20% of patients may have permanent visual impairment. 7 Papillitis is frequently identified in MOGAD, consistent with the anterior visual pathway involvement often seen in this condition. The rate of simultaneous or sequential, bilateral ON is higher than seen in MS or AQP4-NMOSD. Optic neuritis (ON) is the most frequent presentation in adults and children over 9 years. 2,7 A prodromal infection is reported in up to 47% in some studies. The MOGAD clinical phenotype is diverse and varies with age. There are limited reports of association with other autoimmune diseases but fewer than seen with AQP4-NMOSD. There is insufficient data to establish ethnicity or latitude as risk factors. Unlike AQP4-NMOSD and MS, a female preponderance is not evident. 5 Existing cohort studies are small and frequently combine paediatric and adult samples. A recent comparative survey has shown MOGAD is at least twice as common as AQP4-NMOSD. The prevalence of MOGAD is not well established. In MS, lesions are predominantly leukocortical, have a CD8 T-cell infiltrate with chronic radial expansion, whilst in MOGAD plaques are intracortical, associated with a CD4 T-cell inflammatory infiltrate and show preserved AQP4 expression. 2 Pathologically in the brain MOGAD, like MS, shows white matter demyelination characterised by perivenous inflammatory aggregates. MOGAD-like pathology has been induced by encephalitic viruses in transgenic mice expressing MOG antibody. 3 How it bypasses the blood-brain barrier remains unknown. It is likely to be peripherally produced, frequently of the IgG1 isotype, and demonstrates reactivity to an extracellular antigenic region around Proline42 in a large subset of patients. 2 MOG antibody is encephalitogenic in vitro. While its biological role is poorly understood, its association with CNS disease is increasingly apparent. MOG is expressed on the outer sheath of myelin by mammalian CNS oligodendrocytes, prominently exposed to the extracellular space. 1 Recognition of this distinction promotes targeted therapy and prospective research. Its clinical presentation, investigation, management and prognostic considerations distinguish it from multiple sclerosis (MS) and AQP4 antibody associated neuromyelitis optica spectrum disorder (AQP4-NMOSD). Myelin Oligodendrocyte Glycoprotein (MOG) antibody associated disorder (MOGAD) is a unique demyelinating pathology affecting adult and paediatric populations. Here we summarise what is currently known of the pathophysiology, clinical presentation and management of MOGAD. A number of other rare presentations have also been described. Distinct patterns of MOG antibody associated disorder (MOGAD) include acute disseminated encephalomyelitis (ADEM) in children and overlap with neuromyelitis optica spectrum disorders (including classical Devic’s presentations), optic neuritis, transverse myelitis, and focal encephalitis in both children and adults. The advent of more precise live cell-based assays for antibody detection in serum and cerebrospinal fluid (CSF) has greatly refined the clinical phenrotype of demyelinating diseases associated with MOG antibodies. The existence of antibodies to myelin oligodendrocyte glycoprotein (MOG) in some patients with CNS demyelinating disease has been recognised for 30 years, but their clinical utility as biomarkers, and potential pathogenicity in humans has only become apparent in the past 15 years.
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