Atypical clinical manifestation of MT-TL1 mutation in 6 months old patient

The mitochondrial tRNALeu (MT-TL1) m.3243A > G mutation is one of the most frequent pathogenic variants in mtDNA which is associated with various clinical syndromes including Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like episodes (MELAS). The onset of symptoms associated with the MT-TL1 mutation typically occurs in adolescence or early adulthood. Due to the diversity of its clinical presentation, there is a need to report all cases that do not fully meet the criteria of well-established clinical syndromes.

This paper reports a case of a 3-year-old male patient with a complex perinatal history, whose symptoms emerged at 6 months of age and included epileptic seizures, developmental delay, bilateral convergent strabismus, hypertonia, hyperreflexia, and radiological brain abnormalities. The family history is positive for epilepsy and hearing impairment in females on the maternal side. Genetic testing revealed a pathological variant in the MT-TL1 gene m.3243A > G with a high heteroplasmy level of 76.5% in the blood sample.

The case presents an atypical manifestation of the m.3243A > G mutation, highlighting the importance of genetic screening for mitochondrial disorders in patients with a maternal family history.