3-hydroxy-3-methylglutaric aciduria (3HMG) is an organic aciduria, due to deficiency of 3-hydroxy-3-methylglutaryl-CoA-lyase (a key enzyme in ketogenesis and leucine metabolism) usually presenting in infancy with episodes of metabolic decompensation triggered by periods of fasting or infections, which when left untreated are life-threatening and may lead to neurological sequelae. The disease is 3-hydroxy-3-methylglutaric aciduria (MONDO_0009520). Also known as: 3-OH 3-Methyl glutaric aciduria, 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, HMG-CoA lyase deficiency, Hydroxymethylglutaric aciduria, deficiency of hydroxymethylglutaryl-CoA lyase, hydroxymethylglutaryl-CoA lyase deficiency.