• Written By: Michael Vaphiades, DO

    The authors review the general pathophysiological mechanisms underlying neuromyelitis optica (NMO) and the epidemiological, clinical and paraclinical characteristics of seronegative NMO (NMOneg) patients.

    The hallmark of NMO, a rare inflammatory disorder of the central nervous system, is the presence of autoantibodies directed against aquaporin 4 (AQP4-IgG). Despite improvement in the techniques used to detect these antibodies, around 12 to 24% of NMO patients remain seronegative for AQP4-IgG despite a definite diagnosis of NMO.

    NMOneg patients exhibit different demographic and disease-related characteristics than seropositive patients. For example, they have a lower female-male ratio and tend to have a lower relapse rate. However, the authors say that NMOneg patients are probably not a homogenous entity and some could suffer from either atypical acute demyelinating encephalomyelitis or multiple sclerosis.

    Recent studies have found high titers of autoantibodies against myelin oligodendrocyte glycoprotein in NMOneg patients, a key indicator that disease mechanisms might differ in NMOpos and NMOneg. They say this challenges the position of NMOneg patients in the spectrum of demyelinating diseases.

    They argue that a reappraisal of the NMOneg population is needed to improve NMO care. Nonetheless, they note that treatment used for NMOpos appears to be effective for NMOneg. They also say that since NMOneg patients have lower disease activity than NMOpos patients, less aggressive therapies can be used to prevent relapses.