Leigh syndrome, also known as subacute necrotizing encephalopathy, is a neuropathic altered dysfunction that often occurs in infants and young children.First reported by Leigh in 1951, Leigh syndrome is characterized by multiple symmetrical incomplete necrotic lesions (cavernous degeneration) of the brainstem, nucleus accumbens, thalamus, cerebellum, and optic nerves, with a high degree of variability of the clinical picture, which is dependent on the location of the lesioned tissue. Although it may be accompanied by hepatic abnormalities and chronic acidosis, the main features are mental retardation, mental decline, ataxia, optic atrophy, epilepsy, peripheral neuropathies, and brainstem dysfunction, in addition to limb weakness, dystonia, impaired respiratory function, retinitis pigmentosa, and deafness. Acute respiratory failure is a common symptom of Leigh syndrome and may be the first symptom of the patient, with prodromal symptoms such as irregular breathing, sighing breaths, unexplained hyperventilation, or just lethargy. Impaired respiratory function may be due to brainstem involvement, but given that Leigh syndrome can present as a severe myopathy, respiratory failure may also be due to respiratory muscle weakness.Patients with Leigh syndrome also have a number of non-neurologic manifestations, such as endocrine abnormalities (hirsutism, short stature), hypertrophic cardiomyopathy or dilated cardiomyopathy, or gastrointestinal problems (diarrhea). Clinically, coenzyme Q deficiency can also present as Leigh syndrome, which can have congenital hypotonia, secondary epilepsy, progressive limb weakness, feeding difficulties, episodes of vomiting, which can be exacerbated by hypo-proteinemic edema, and ultimately can lead to death, but blood lactate levels are generally normal in the disease, and there is no imaging typical of Leigh syndrome. Coenzyme Q supplementation can greatly improve the symptoms, and blood genetic analysis and muscle biopsy can differentiate between the two. Plasma and cerebrospinal fluid lactate levels are usually elevated in patients with Leigh syndrome. Hyperlactatemia may not be apparent in the early stages of the disease, but may develop as the disease progresses. Patients with skeletal muscle involvement may also have elevated muscle enzymes, particularly creatine kinase. Most patients have typical MRI findings (midbrain, basal ganglia, and brainstem T2MRI high signal with or without cortical changes). Brain histopathology shows brainstem spongiform degeneration with neuronal loss and vascular proliferation in the basal ganglia, thalamus, and cerebellum; the cortex of the cerebrum and cerebellum is unaffected. Leigh syndrome is usually a metabolic encephalopathy occurring in infancy and childhood, with adult-onset patients being rare. Patients with adult-onset disease may present with typical symptoms of Leigh syndrome or with more complex and varied symptoms. The diagnosis of Leigh syndrome requires (1) progressive psychomotor retardation, (2) signs or symptoms of damage to the brainstem or basal ganglia, (3) elevated blood or cerebrospinal fluid levels of lactic acid, and (4) neuroimaging features (symmetric hypodense shadows of the basal ganglia on CT, symmetric hyperdense shadows of the basal ganglia on MRI) or typical pathological changes in the brain tissue or a clear family history. There is no treatment for the cause of the disease.Patients with Leigh syndrome may benefit from receiving high doses of thiamine, coenzyme Q, or L-carnitine. However, vitamin C/E and L-carnitine are not effective in patients if they carry a mutation in the surf1 gene. Other than that, the main focus is on symptomatic treatment, taking the necessary steps to save the patient’s life in case of respiratory failure, heart failure or kidney failure.