Natural History Study of FDXR Mutation-related Mitochondriopathy

Inclusion Criteria: * Patients who are clinically diagnosed with biallelic mutations in the ferredoxin reductase gene * Male and female patients from 2 to 65 years of age * Patients who have consented to the study * In the case of a deceased patient whose parent(s) and/or legal guardian(s) have provided informed consent for study participation, the investigators will review the patient's medical records to determine study eligibility. Exclusion Criteria: * Significant postnatal complications or congenital anomalies that are not known to be associated with ferredoxin reductase deficiency * Patient has received any experimental treatment for ferredoxin reductase deficiency within the 6 months prior to enrollment, or is expected to receive any such therapy during the study period