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 1-8 years (median 4 years). 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 7 years [interquartile range (IQR) 4-11 years]. 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 12 years 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.