Summary: The main goal of the project is provison of a global registry for mitochondrial disorders to harmonize previous national registries, enable world-wide participation and facilitate natural history studies, definition of outcome measures and conduction of clinical trials.

Summary: This is a multi-center natural history study of Mitochondrial NeurogastroIntestinal Encephalopathy (MNGIE). Patients will be followed over time to assess clinical symptoms. The investigators hope to learn more about the disease of MNGIE as well as develop useful measures of disease status for use in future clinical trials. Additional clinical centers will be listed as they become available.

Summary: Carriers of the m.3242A>G mutation often have clinical symptoms which can include migraines, seizures, strokes, hearing loss, balance issues, gastrointestinal issues, and many other symptoms. The investigators would like to learn more about these disorders and have designed a Natural History Study to monitor these conditions over time so that physicians and scientists can not only understand the p...

Summary: Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are a genetically and clinically heterogeneous group of autosomal recessive disorders that are characterized by a severe reduction in mtDNA content leading to impaired energy production in affected tissues and organs. MDS are due to defects in mtDNA maintenance caused by mutations in nuclear genes that function in either mitochondrial nucleotide ...

Summary: This is an open-label, multi-centre study in subjects with a genetically confirmed mitochondrial deoxyribonucleic acid (DNA) transfer ribonucleic acid (tRNA)Leu(UUR) m.3243A>G mutation who completed study KH176-202. In the KH176-203 study subjects will be receiving KH176 100 mg BID or KH176 50 mg bid in die (BID) (as determined by the investigator based on safety / tolerability considerations) for...

Summary: The purpose of this study is to develop a database containing clinical and laboratory information for patients with Leigh syndrome. The goal is to provide a greater understanding of Leigh syndrome allowing further characterization of this disease.

Summary: The main purpose of this study is to determine the safest maximum dose of an amino acid, citrulline, which will be used as potential treatment for adult patients with a disorder of energy metabolism called Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS). Once established, this dose will be used in a future clinical trial.