a rare heteroplasmic mt-nd5 mutation (m.13094t>c) in an iranian patient with adult-onset melas: diagnostic challenges and therapeutic implications

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes [melas] is a rare multisystem mitochondrial cytopathy that is highly heterogeneous in severity and clinical presentation, mostly caused by diverse mutations in the mitochondrial dna. while m.3243a>g is the most common variant, rare mutations like m.13094t>c in mt-nd5 are increasingly recognized but poorly characterized. this report documents the case of a 37-year-old iranian woman diagnosed with melas. her clinical manifestations include recurrent episodes of stroke-like events, focal seizures, and elevated serum and csf lactate. mitochondrial dna analysis [mtdna] was positive for a very rare pathogenic point mutation [mtdna; m.3243a>g] in the mt-nd5 gene, with a heteroplasmy level of 8.2%. this case highlights: 1. adult-onset melas with mt-nd5 mutations is underdiagnosed. 2.low heteroplasmy (8.2%) may still cause severe phenotypes, suggesting tissuespecific effects. 3.ethnic diversity in mtdna mutations warrants broader genetic screening in non-classical cases.