Late-onset neuromyelitis optica spectrum disorder in AQP4-seropositivepatients in a Chinese population

Background: Increasing rates of AQP4-seropositive neuromyelitis optica spectrum disorder (NMOSD) have been reported in late-onset patients (LONMOSD). However, the full range of clinical differences between early-onset and late-onset variants remain unclear. We describe the clinical features and outcomes of AQP4-seropositive LONMOSD patients in a Chinese population. Methods: This was a retrospective analysis of medical records in a cohort study of AQP4-seropositive NMOSD patients with early-onset (<= 49 years) and late-onset (>= 50 years) variants between January 2006 and February 2014. Demographic, clinical, neuroimaging and cerebrospinal fluid (CSF) findings and prognosis data were analyzed. Results: We identified thirty AQP4-seropositive LONMOSD patients (86.7 % women). The median age at onset was 57.5 years (range 50-70). There were similar onset frequencies between optic neuritis (ON) and longitudinally extensive transverse myelitis (LETM). Longer interval between (first) ON and LETM (median 13 vs. 4 months; p < 0.05), time from first symptoms to diagnosis of NMO (median 17 vs. 7 months, p < 0.05), higher comorbidities (66.7 vs. 26.7 %; p < 0.05), and more hypertension (26.7 vs. 3.3 %; p < 0.05) were prevalent. NMO-like lesions were less common (10.7 vs. 41.6 %; p < 0.05), while the rate of non-specific lesions tended to be higher (53.6 vs. 29 %; p = 0.067). These patients displayed more severe Expanded Disability Status Scale (EDSS) in nadir (median 6.75vs. 5; p < 0.05). Attacks often resulted in EDSS 4 within a short period (median 8 vs. 13.5 months; p < 0.05). At last follow-up, the EDSS score was more severe in these patients (median 5.25 vs. 4; p < 0.05). No significant predictors were identified. Conclusions: This study provides an overview of the clinical and paraclinical features of AQP4-seropositive LONMOSD patients in China and demonstrates a number of distinct disease characteristics in early vs. late onset. Older patients are more susceptible to disability in short course. However, these patients do not always display NMO-like lesions in the brain. Initial LETM may not necessarily be predominant as the initial symptom, contrary to previous reports. The higher comorbidities may warrant a modified approach of treatment.