Defects in ISCA1, ISCA2 and IBA57 have been associated with numerous mitochondrial diseases now categorized as multiple mitochondrial dysfunctions syndromes MMDS3 (IBA57) [80,81,187], MMDS4 (ISCA2) [79], and MMDS5 (ISCA1) [77,78]. This evidence concerns the gene ISCA2 and Fatal multiple mitochondrial dysfunction syndrome type 2.