Introduction Around 70–90% of typical NMO have aquaporin-4 antibodies (AQP4-Ab). More recently, an association between myelin oligodendrocyte glycoprotein antibodies (MOG-Ab) and monophasic NMO has been reported.

Methods We present 5 AQP4-Ab negative cases with relapsing CNS demyelinating disease (4 with NMO phenotype) associated with MOG-Ab.

Results All patients were Caucasian. Four patients presented with typical NMO phenotype. One patient had a long myelitis and a further brainstem event. Median age at onset was 17 (16–39) years. The first episode of optic neuritis and longitudinally extensive myelitis developed simultaneously in 2 patients while 2 patients had inter-attack interval 1.1 and 7 years. All except one patient had a normal brain MRI. EDSS (visual) scores after disease duration (number of relapses) of 1.3 (2), 1.6 (2), 3.4 (6), 8.3 (7) and 12 (13) years were 5 (0), 4 (3), 3 (5), 4 (0) and 4 (6) respectively.

Conclusions MOG-Ab can be seen in relapsing NMO and is not restricted to the monophasic subtype. The clinical and diagnostic role of MOG-Ab is still evolving.