Monarch Disease Ontology id MONDO_0009723 (Leigh syndrome) is a progressive neurological disease defined by specific neuropathological features associating brainstem and basal ganglia lesions. Also known as: LS, LSS, Leigh disease, Leigh syndrome spectrum, Leigh's disease, infantile necrotizing encephalomyelopathy, infantile subacute necrotizing encephalopathy, juvenile subacute necrotizing encephalomyelopathy.