OBSOLETE: Sporadic Leigh syndrome

Sporadic Leigh syndrome (Orphanet code 255199) was a clinical designation used to describe cases of Leigh syndrome (also known as subacute necrotizing encephalomyelopathy) that occurred without a clear familial or inherited pattern. Leigh syndrome is a severe progressive neurological disorder characterized by bilateral symmetric necrotic lesions in the brainstem, basal ganglia, thalamus, and spinal cord, typically visible on brain MRI. It primarily affects the central nervous system and is caused by defects in mitochondrial energy metabolism. This Orphanet entry is now classified as OBSOLETE, meaning it is no longer maintained as a distinct clinical entity. Cases previously categorized under this term have been reclassified under broader Leigh syndrome entries, as advances in genetic testing have revealed that most apparently 'sporadic' cases do in fact have identifiable genetic causes — whether nuclear gene mutations (autosomal recessive or X-linked) or mitochondrial DNA mutations. Key symptoms of Leigh syndrome include psychomotor regression, hypotonia, dystonia, ataxia, respiratory abnormalities, feeding difficulties, lactic acidosis, and failure to thrive. The disease predominantly presents in infancy or early childhood, though later-onset forms exist. There is no cure for Leigh syndrome. Treatment remains largely supportive and symptomatic, including nutritional support, management of metabolic crises, and physical therapy. Some patients may receive cofactor supplementation (such as thiamine, coenzyme Q10, or riboflavin) depending on the underlying biochemical defect, though evidence for efficacy is limited. Prognosis is generally poor, with many affected children experiencing progressive neurological decline.

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