An Observational Study of Patients With Primary Mitochondrial Disease (SPIMM-300)

Inclusion Criteria: * Willing and able to provide a signed informed consent form (ICF) prior to participation in any-trial related procedures * Patient has clinical presentation of PMD with either signs or symptoms suggestive of myopathy * Patient is ambulatory and able to attempt 6MWT Exclusion Criteria: * Patient has symptoms of PMD due to secondary mitochondrial dysfunction * Patient has had prior exposure to elamipretide * Patient does not have the cognitive capacity to understand and complete all study assessments * Patient has a medical history of severe renal impairment * History of active alcoholism or drug addiction during the year before enrollment