In patients with French-Canadian Leigh Syndrome (LSFC), which is an autosomal recessive OXPHOS disorder caused by a mutation of the LRPPRC gene, the assembly of all ETC complexes is disrupted, with the exception of the nuclear-encoded subunits of CII and CV, which results in normal SDHA levels in patients. Here, LRPPRC is linked to congenital lactic acidosis, Saguenay-Lac-Saint-Jean type.