FDX2 and lactic acidosis: The first case of mitochondrial myopathy associated with FDX2 was described in 2014 in a 15-year-old patient with recurrent myoglobinuria, lactic acidosis, and slowly progressive muscle weakness due to a homozygous mutation affecting the translation start codon of FDX2 (c.1 A > T, p.Met1Leu) and resulting in a severe decrease in FDX2 protein [1].