Such an increase in lipid droplets, potentially related to a lipid metabolism defect, was also recently observed in a 12-y-old girl exhibiting progressive muscle degeneration and autoimmune polyendocrinopathy and was determined to have cosegregating mutations in MARS2's cognate tRNA, mitochondrial tRNAmethionine, as well as COX III [74], as well as in patients with other mitochondrial diseases such as Leigh Syndrome, Alpers Disease, and Lethal Infantile Mitochondrial Disease [75]. This evidence concerns the gene MARS2 and mitochondrial DNA depletion syndrome 4a.