The phenotypic spectrum of the idiopathic inflammatory demyelinating disorders of the central nervous system (CNS) suggests that neuromyelitis optica (NMO), which includes Devic’s disease, is a distinct clinical entity separate from classic or conventional multiple sclerosis.¹ NMO is also phenotypically similar to the optico-spinal form of multiple sclerosis (OSMS) that occurs commonly in Asian populations with multiple sclerosis.² NMO and OSMS, by definition, involve the optic nerves and spinal cord. They tend to be severe diseases, typically causing complete transverse myelitis associated with longitudinally extensive lesions, as seen on magnetic resonance imaging (MRI), which may evolve to form a syrinx. An MRI of the brain is typically normal. NMO is often associated with a mild cerebrospinal fluid (CSF) pleocytosis, which is often polymorphonuclear in nature. Locally synthesised oligoclonal immunoglobulin G (IgG) bands are typically absent in NMO.¹ Pathologically, NMO is characterised by necrosis, eosinophilic and neutrophilic infiltrates, vascular proliferation, and hyalinisation and complement activation in a perivascular “rosette” pattern.^1,3 These clinical and pathological features are uncommon in patients with multiple sclerosis.³

In 2004, the Mayo Clinic group, by using …