Diagnostic pitfalls in neuromyelitis optica spectrum disorders

Neuromyelitis optica spectrum disorders are autoimmune disorders of the central nervous system marked by inflammatory demyelination, axonal loss and astrocytopathy, associated with lesions in the brain and in the spinal cord and with the presence of antibodies against aquaporin 4 (AQP4-IgG). Various studies on neuromyelitis optica spectrum disorders broaden the knowledge about their immunopathogenesis, clinical course, immunological assays, and magnetic resonance imaging findings. Nevertheless, in clinical practice differential diagnosis remains challenging, particularly in cases seronegative for AQP4-IgG. Essential clinical syndromes in neuromyelitis optica spectrum disorders, namely optic neuritis and acute myelitis, could also be observed in multiple sclerosis and other demyelinating diseases of the central nervous system. The early and accurate diagnosis is essential due to different prognosis and treatment strategies in these diseases. For example, therapies used in multiple sclerosis, including beta-interferons, natalizumab, fingolimod and alemtuzumab, may not only be ineffective in neuromyelitis optica spectrum disorders but even harmful and provoke relapses. Therefore, in a patient with a clinical neurological syndrome accompanied by demyelinating lesions in the central nervous system several investigative studies should be undertaken, including serological assays [AQP4-IgG, antibodies against myelin oligodendrocyte glycoprotein (MOG-Ab)], the cerebrospinal fluid examination and magnetic resonance imaging of the brain and spinal cord, and interpreted with caution. Due to clinical similarities and relatively common misdiagnoses, there is a need to summarise the typical and atypical clinical, laboratory and radiographic features in neuromyelitis optica spectrum disorders to avoid diagnostic pitfalls and inappropriate treatment.