MEGDEL is an autosomal recessive disorder characterized by childhood onset of delayed psychomotor development or psychomotor regression, sensorineural deafness, spasticity or dystonia, and increased excretion of 3-methylglutaconic acid. Brain imaging shows cerebral and cerebellar atrophy as well as lesions in the basal ganglia reminiscent of Leigh syndrome. Laboratory studies show increased serum lactate and alanine, mitochondrial oxidative phosphorylation defects, abnormal mitochondria, abnormal phosphatidylglycerol and cardiolipin profiles in fibroblasts, and abnormal accumulation of unesterified cholesterol within cells. About 50% of patients develop severe, but transient, liver dysfunction and/or signs of liver failure, in the neonatal period or during the first year of life, prompting some authors to suggest the name 'MEGDHEL' syndrome, with the 'H' referring to 'hepatopathy'. Some patients may have a milder presentation with juvenile-onset spasticity and mild cognitive impairment, indicating a broader phenotypic spectrum. [From OMIM]