Collection of Blood and Skin Samples From Patients With Primary Mitochondrial Diseases and Healthy Volunteers

Inclusion Criteria: 1. Male or female, age 3 to 85 years. 2. For patients with Primary Mitochondrial Disease: a. Clinical diagnosis of PMD confirmed by mtDNA sequencing. 3. For Healthy Volunteers: 1. Normal Vital signs and BMI for age 2. No active medical conditions or diseases 3. No current medications, other than acetaminophen and naproxen sodium 4. For All Subjects: 1. No viral or bacterial illness in past 2 weeks 2. No antibiotic or antiviral medications in past 2 weeks 3. No blood transfusion in past 2 weeks 4. No current pregnancy 5. Not currently breastfeeding 6. Alcohol use less than 2 drinks / day 7. No recreational or illicit drug use in previous 1 year 8. No tobacco or nicotine containing products in previous 1 year 5. Patient, parent or guardian able to understand and provide voluntary written informed consent. Exclusion Criteria: 1\. History of prior treatment with allogeneic hematopoietic stem cell transplantation, or gene therapy.