The NIH MINI Study: Metabolism, Infection, and Immunity in Inborn Errors of Metabolism

* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: 1. Stated willingness to comply with all study procedures and availability for the duration of the study. 2. Male or female, \>4 weeks of age. 3. Diagnosis of mitochondrial disease with documented molecular evidence of disease. 4. Healthy volunteers of any gender and ethnicity \>2 years of age may also be eligible to enroll in the protocol. Healthy volunteers may be from the local community, or family members of patients with MtD. 5. Agreement to adhere to Lifestyle considerations throughout study duration. 6. Ability of subject or Legally Authorized Representative (LAR) to understand and the willingness to sign a written informed consent document. Overall, most participants will be over the age of 2 years. Advances in genetic diagnostics coupled with earlier diagnosis of MtD has led to an increasing number of participants who could be eligible within the 1-24 month age range. Participants with MtD who are between 1-24 months of age may be enrolled on this study on a case by case basis at the discretion of the PI and clinical team. The participants clinical status and resource availability within NIH will be taken into account. The majority of the clinical team, has pediatric experience and/or are board certified in Pediatrics (PI) or Pediatric Neurology (Staff Clinician). Participants with a hospitalization immediately prior to their appointment date will be rescheduled. Rescheduled appointments will occur no earlier than 2 weeks after the hospitalization discharge date. The enrollment is requested to be 50/year with a ceiling of 500 participants: 300 MtD participants and 200 healthy volunteers. Enrollment is anticipated to be up to 50 MtD participants/year and up to 30 HV/year. Recruitment of healthy volunteers may be targeted to match age ranges and sex of MtD participants seen. We may also receive deidentified biospecimens (blood spots, blood samples, serum samples) from biorepositories such as the National Children s Study, the Mitochondrial Disease Biobank at Mayo, the biorepository at the Children s Hospital of Philadelphia, or the North American Mitochondrial Disease Consortium, to our current protocol. These samples may be used to examine the role of mitochondrial haplogroups, ancient mutations in mtDNA that help define ancestral origins, in mitochondrial disease, as well as nDNA mutations involved in mitochondrial disease. Under an MTA, we are requesting biospecimens for up to 500 participants, which will be stored indefinitely or until use. Our recruitment will remain the same since these are specimens only and not additional participants. For the Mitochondrial Disease Biobank, we mayrequest materials and patient clinical information for up to 500 individuals to help supplement our current cohort. EXCLUSION CRITERIA: An individual who meets any of the following criteria will be excluded from participation in this study: 1. Lack of a local MtD provider (For participants with MtD only) 2. Pregnancy or lactation 3. Discretion and clinical judgement of the Principal Investigator