Survival analysis of a cohort of Chinese patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) based on clinical features

Background: Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is a common mitochondrial syndrome. The aim of this study was to conduct a survival analysis based on the clinical features of a Chinese MELAS patient cohort.

Methods: This is a retrospective single-center study. The MELAS patients were followed up for 1-8years (median 4years). The disease severity was evaluated by the modified Rankin Scale (mRS). The survival analysis was performed using Kaplan-Meier analysis and Cox proportional hazards model.

Results: A total of 138 subjects were enrolled, and the median disease duration was 7years [interquartile range (IQR) 4-11years]. The stroke-like episodes were the most common initial symptoms (70.3%). Seventeen (17.3%) subjects lost to follow-up. Of the 121 subjects who successfully completed the follow-up, 28 subjects died (mortality rate 23.1%). An acute stroke-like episode and/or status epilepticus were the predominant causes of death (42.9%). Among the surviving patients (n=93), 39.8% (37/93) required assistance in daily life (mRS scores 3-5). The mRS scores were inversely correlated with the age of onset (r=-0.28, P=0.0022) but not with the disease duration (r=0.10, P=0.2709). The survival rate declined mainly within 12years after the disease onset. The stroke-like episode as the initial symptom was an independent risk factor for death (hazard ratio=2.86, 95% CI 1.03-7.94, P=0.043).

Conclusions: MELAS had high mortality and morbidity in this cohort of Chinese patients. The early onset of stroke-like episodes might indicate the more severe form of the disease, highlighting the importance of management of stroke-like episodes to improve the prognosis.