Mitochondrial disorders are one of the most challenging collections of human diseases impacting nearly 1:4000 live births (Vafai and Mootha 2013; Stewart and Chinnery 2015) and often affect the nervous system. Most of these disorders are due to biochemical lesions in the oxidative phosphorylation (OXPHOS) system, the organelle’s core pathway responsible for making adenosine triphosphate (ATP) by consuming the oxygen we breathe. The OXPHOS system is encoded both by the nuclear and mitochondrial (mtDNA) genomes. To date, nearly 250 different monogenic forms of mitochondrial disease, involving both genomes, have been described. Each one impacts a different subset of organ systems. The genetic, biochemical, and clinical heterogeneity has made the diagnosis and management of these disorders incredibly difficult, since no two cases present identically.