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.

Leigh syndrome, also known as juvenile sub-acute necrotizing encephalopathy, is a progressive neurodegenerative disorder associated with dysfunction of mitochondrial oxidative phosphorylation (OXPHOS). First described in 1951 by British neuropsychiatrist Archibald Denis Leigh, the condition has evolved from a post mortem diagnosis to a clinical entity with characteristic radiologic and laboratory findings.

Leigh syndrome is a rare and heterogeneous disease, finding a substantial number of patients to study is difficult. The lack of natural history data in Leigh syndrome and the small number of patients included in clinical reports thus far has limited the ability to fully comprehend the progression of this disease and assess prognostic factors. A Leigh syndrome database will help improve our understanding of this rare disease leading to an improved ability to predict outcomes and/or improve treatment paradigms. Collecting natural history data on Leigh syndrome and integrating this information into a database will be useful in understanding the course of the disease and identifying trends.

Inclusion Criteria:

• All participants with a diagnosis of Leigh syndrome will be invited to participate

Exclusion Criteria:

• People without Leigh syndrome

People with a diagnosis of Leigh syndrome.