Acute Infection in Mitochondrial Disease: Metabolism, Infection and Immunity

* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: Group 1a 1. Participants must be two months of age or older. 2. Participants must have a diagnosis of mitochondrial disease based on a determination by a physician with expertise in genetics and/or neurology. Supportive evidence may include genetic testing, muscle biopsy, biochemical testing, neuroimaging or enzyme analysis consistent with mitochondrial disease. 3. At the time of enrollment, participants must have suspected or confirmed acute infection as defined by 1. New onset of any of the following symptoms within one month of enrollment without an alternative diagnosis: fever, cough, shortness of breath, fatigue, sore throat, rhinorrhea, musculoskeletal pain, vomiting, diarrhea, anosmia, neurologic decline; AND report that testing for infection (e.g. respiratory viral panel, SARS15 COV-2 testing) is clinically indicated based on evaluation by a healthcare provider. OR 2. Laboratory confirmed positive testing for an infectious disease as performed at a local healthcare setting. Note: At the time of initial approval of this protocol, testing for COVID-19/SARSCov-2 was not consistently available. In order to avoid bias by limiting recruitment to only those individuals with access to these healthcare resources, inclusion criteria for participants with acute illness were intentionally kept broad. Participants in Group 1 who were initially suspected to have COVID-19 but later found to have an alternative infectious illness were used for comparison studies. In 2023, after the end of the COVID-19 emergency, inclusion criteria for this study were broadened to focus on all acute infections in mitochondrial disease in order to characterize relationships between specific pathogens, immunophenotypes and clinical phenotypes in mitochondrial disease. Please also note that there is no minimum weight requirement for Group 1. However, there is a minimum weight requirement for phlebotomy procedures. Group 1 participants who do not meet minimum weight requirements may enroll for records and questionnaires only. Group 1b 1. Participants must be two months of age or older. 2. Participants must have a diagnosis of mitochondrial disease based on a determination by a physician with expertise in genetics and/or neurology. Supportive evidence may include genetic testing, muscle biopsy, biochemical testing, neuroimaging or enzyme analysis consistent with mitochondrial disease. 3. At the time of enrollment, participants may not have evidence of any acute infection. Note: Some participants may initially enroll in Group 1b and later experience acute infection, in which case they may be moved from Group 1b to Group 1a. Group 2 1. Participants must be two months of age or older. 2. Participants must weigh greater than 4 kilograms. 3. Participants must be household or family member of a participant in Group 1 above. EXCLUSION CRITERIA: An individual who meets any of the following criteria will be excluded from participation in this study: Groups 1 a\&b 1. Participants who are less than two months of age. 2. Participants who do not have mitochondrial disease. 3. Study team may decline to enroll a participant for other reasons based on clinical judgement. Group 2 1. Participants who are less than two months of age. 2. Participants who are not household or family members of Group 1. 3. Study team may decline to enroll a participant for other reasons based on clinical judgement.