Molecular and neurological features of MELAS syndrome in paediatric patients: A case series and review of the literature.

Background: Mitochondrial encephalomyopathy, lactic acidosis and stroke‐like episodes (MELAS) syndrome is one of the most well‐known mitochondrial diseases, with most cases attributed to m.3243A>G. MELAS syndrome patients typically present in the first two decades of life with a broad, multi‐systemic phenotype that predominantly features neurological manifestations––stroke‐like episodes. However, marked phenotypic variability has been observed among paediatric patients, creating a clinical challenge and delaying diagnoses. Methods: A literature review of paediatric MELAS syndrome patients and a retrospective analysis in a UK tertiary paediatric neurology centre were performed. Results: Three children were included in this case series. All patients presented with seizures and had MRI changes not confined to a single vascular territory. Blood heteroplasmy varied considerably, and one patient required a muscle biopsy. Based on a literature review of 114 patients, the mean age of presentation is 8.1 years and seizures are the most prevalent manifestation of stroke‐like episodes. Heteroplasmy is higher in a tissue other than blood in most cases. Conclusion: The threshold for investigating MELAS syndrome in children with suspicious neurological symptoms should be low. If blood m.3243A>G analysis is negative, yet clinical suspicion remains high, invasive testing or further interrogation of the mitochondrial genome should be considered. [ABSTRACT FROM AUTHOR]