Relatively little is known so far about leptomeningeal involvement in MOG-IgG-positive myelitis.<h4>Findings</h4>We report the case of a 30-year-old previously healthy woman presenting with longitudinally extensive transverse myelitis and tetraparesis, in whom both the leptomeningeal barrier and the blood-brain barrier (BBB) were altered, as demonstrated by gadolinium-enhanced MRI during relapse. Here, MOG is linked to myelitis.