Leber hereditary optic neuropathy (LHON) is a mitochondrial disorder characterized by subacute visual loss, typically linked to genetic defects affecting respiratory complex I genes. Here, we expand the genetic landscape of LHON by describing the first autosomal recessive case with pathogenic variants in the MECR gene. The MECR enzyme belongs to the mitochondrial fatty acid synthesis (mtFAS) pathway, thus breaking the paradigm that LHON is exclusively associated with complex I dysfunction. Last, the clinical course of the reported patients introduces the new feature of recurrence of visual loss, which does not occur in classic mtDNA-related LHON. (https://jmg.bmj.com/content/early/2023/09/20/jmg-2023-109340 )