The enzyme called 3-Methyl Glutaconyl-CoA Hydratase is involved in amino acid (Leucine) metabolism. This enzyme is located in the mitochondria together with other enzymes of catabolic leucine. When an individual has a deficiency of 3-Methyl Glutaconyl-CoA Hydratase, 3-methylglutaconic acid is excreted massively and the impaired leucine breaks down. Very few patients have been reported with this type of deficiency but its occurrence is a reality, nonetheless. There a few severe clinical cases that have been reported which resulted because of this deficiency. Some patients have developed severe cardiopulmonary manifestations as soon as they were born; others have been reported to have psychomotor retardation; other cases include hypotonia, seizures, spasticity and thriving failure. Carnitine levels are at their lowest with this deficiency occurs. There are also rare cases of recurrent acidosis (seen in cases of fasting that has been prolonged). There was also a reported case of speech retardation.