Although complex II deficiencies are exceedingly uncommon (almost 2–8% of mitochondrial disease cases), either homozygous or heterozygous pathogenic variants are reported in SDHA, SDHB, and SDHD genes, leading to some primary mitochondrial disease such as Leigh or Leigh-like syndrome [60]. The gene discussed is SDHD; the disease is inborn mitochondrial metabolism disorder.