Leigh syndrome is a major phenotype of mitochondrial diseases in children. With new therapeutic options being proposed, assessing the mortality and clinical condition of Leigh syndrome patients is crucial for evaluating therapeutics. As data are scarce in Japan, we analysed the mortality rate and clinical condition of Japanese Leigh syndrome patients that we diagnosed since 2007. Data from 166 Japanese patients diagnosed with Leigh syndrome from 2007 to 2017 were reviewed. Patients' present status, method of ventilation and feeding, and degree of disability as of April 2018 was analysed. Overall, 124 (74.7%) were living, 40 (24.1%) were deceased, and 2 (1.2%) were lost to follow‐up. Median age of living patients was 8 years (1‐39 years). Median length of disease course was 91 months for living patients and 23.5 months for deceased patients. Nearly 90% of deaths occurred by age 6. Mortality rate of patients with onset before 6 months of age was significantly higher than that of onset after 6 months. All patients with neonatal onset were either deceased or bedridden. MT‐ATP6 deficiency caused by m.8993T>G mutation and MT‐ND5 deficiency induced a severe form of Leigh syndrome. Patients with NDUFAF6 , ECHS1 , and SURF1 deficiency had relatively mild symptoms and better survival. The impact of onset age on prognosis varied across the genetic diagnoses. The clinical condition of many patients was poor; however, few did not require mechanical ventilation or tube‐feeding and were not physically dependent. Early disease onset and genetic diagnosis may have prognostic value.

中文翻译：

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日本 Leigh 综合征患者的死亡率：发病年龄和基因诊断的影响。

Leigh 综合征是儿童线粒体疾病的主要表型。随着新的治疗方案的提出，评估 Leigh 综合征患者的死亡率和临床状况对于评估治疗方法至关重要。由于日本的数据稀缺，我们分析了自 2007 年以来诊断出的日本 Leigh 综合征患者的死亡率和临床状况。回顾了 2007 年至 2017 年诊断出的 166 名日本 Leigh 综合征患者的数据。分析了截至 2018 年 4 月患者的现状、通气和喂养方法以及残疾程度。总体而言，124 人（74.7%）健在，40 人（24.1%）已故，2 人（1.2%）失访。存活患者的中位年龄为 8 岁（1-39 岁）。存活患者的中位病程长度为 91 个月，死亡患者的中位病程长度为 23.5 个月。近90%的死亡发生在6岁之前。6个月前发病的患者死亡率明显高于6个月后发病的死亡率。所有新生儿发病患者均已死亡或卧床不起。由 m.8993T>G 突变和MT-ND5缺乏引起的MT-ATP6缺乏会导致严重的 Leigh 综合征。患者NDUFAF6，ECHS1和SURF1缺乏有症状比较轻和更好的生存。发病年龄对预后的影响因基因诊断而异。许多患者的临床状况不佳；然而，很少有人不需要机械通气或管饲，也没有身体依赖。早期发病和基因诊断可能具有预后价值。