Background: Leigh Syndrome (LS) is a severe neurodegenerative disorder characterized by bilateral symmetrical necrotic lesions in the basal ganglia and brainstem. Onset is in early infancy and prognosis is poor. Causative mutations have been disclosed in mitochondrial DNA and nuclear genes affecting respiratory chain subunits and assembly factors.
Case presentation: Here we report the clinical and molecular features of a 15-month-old female LS patient. Direct sequencing of her muscle-derived mtDNA revealed the presence of two apparently homoplasmic variants: the novel m.14792C>G and the already known m.14459G>A resulting in p.His16Asp change in cytochrome b (MT-CYB) and p.Ala72Val substitution in ND6 subunit, respectively. The m.14459G>A was heteroplasmic in the mother's blood-derived DNA.
Conclusions: The m.14459G>A might lead to LS, complicated LS or Leber Optic Hereditary Neuropathy. A comprehensive re-evaluation of previously described 14459G>A-mutated patients does not explain this large clinical heterogeneity.