Different immunological status and pathophysiologies exist between NMO and MS, and IL-6 may play important roles in the pathogenesis of NMO.

Patients receiving etoposide within four weeks after diagnosis had a good prognosis as five of the seven patients survived compared to one of 13 not treated with etoposide or treated late (chi-square test for survival, P = 0.0095). The Kaplan-Meier analysis showed the 2.5-year survival of 85.7 +/- 13.2% in the early etoposide-treated patients, compared to 10.3 +/- 9.4% in the remaining patients (log-rank test, P = 0.0141). Thus, early etoposide treatment is effective in treating EBV-HLH in young adults as well as in children.

IFNB-1b treatment does not appear to be effective for preventing relapse in NMO likely because of differences between the immune-pathogenesis of NMO and MS.

To investigate differences in helper T cell immune responses in cerebrospinal fluid (CSF) between neuromyelitis optica (NMO) and multiple sclerosis (MS), we measured CSF levels of interleukin (IL)-2, IL-4, IL-6, IL-10, tumor necrosis factor-a and interferon-c at the time of relapse in 17 NMO patients and 21 MS patients using fluorescence-activated cell sorting. CSF IL-6 levels were significantly higher in NMO patients than in patients with MS (P = 0.001) and other neurological diseases (P = 0.001). The other cytokines tested were undetectable. Elevated CSF levels of IL-6 in only NMO supports the view of different pathophysiologies of NMO and MS. CSF IL-6 levels may be useful in the differential diagnosis of the two disorders.

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