Clinical, imaging, muscle pathological and gene mutational features of patients with late-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes / 中华神经医学杂志

ABSTRACT

Objective:To summarize the clinical, imaging, muscle pathological and gene mutational features of patients with late-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).Methods:Three patients with late-onset MELAS, admitted to Department of Neurology, Jiaozuo People's Hospital Affiliated of Xinxiang Medical University from January 1997 to December 2021 were chosen; all patients were screened for mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) mutations by second-generation gene sequencing. The clinical, imaging, muscle pathological and gene mutational features of patients with late-onset MELAS were analyzed retrospectively.Results:The main clinical manifestations of these late-onset MELAS patients included stroke-like attacks, headache, hearing and vision loss, cognitive decline and mental disorder. The muscle tension and muscle strength of both upper extremities in these 3 patients were normal. Increased muscle tension and active tendon reflexes, and positive pathological signs in both lower extremities were noted in 2 patients. Head MRI showed abnormal long T1 and long T2 signals in temporal occipital parietal cortex and subcortex in 3 patients, and CT showed calcification in bilateral globus pallidus in 1 patient. Ragged red fibers (RRF) and ragged blue fibers (RBF) were found in the muscle biopsies of 3 patients, and cytochrome oxidase (COX)-negative muscle fibers were found in 2 patients. MT-TL1 gene m.3243A>G mutation was detected in all 3 patients by genetic testing, among which mutation in the blood of 2 patients was 15% and 17%, respectively, and mutation in the muscle tissues of 1 patient was 73%. Conclusion:Muscle pathology indicates high RRF percentage in patients with late-onset MELAS; and m.3243A>G spot mutation is the most common mutation type in late-onset MELAS, and m.3243A>G mutation ratio in muscle tissues is obviously higher than that in blood.