Leigh disease, also known as subacute necrotizing encephalopathy, is a rare genetic disorder that affects the central nervous system. It's a progressive disorder that usually develops in infants and young children. The disease is caused by a deficiency in mitochondrial enzymes and can lead to motor problems, developmental delays, seizures, and respiratory issues. There are several synonyms for Leigh disease, which include Leigh syndrome, infantile subacute necrotizing encephalomyelopathy, and subacute necrotizing encephalopathy. These terms are used interchangeably to describe the same condition, which is caused by mitochondrial dysfunction. The severity of the disease varies from person to person, and early diagnosis and treatment are essential in managing the symptoms and improving the quality of life for those affected by Leigh disease.