... Defect in an enzyme that activates several other enzymes, leading to buildup of lactic acid and other organic acids. Untreated, can cause brain damage, coma, and death. Symptoms, including ... Untreated, can lead to brain damage, mental retardation, coma, and death. Treatment includes a diet low in protein and fat, and high in carbohydrates.Multiple carboxylase deficiency (<1 in 100,000). ... DisordersIsovaleric acidemia (<1 in 100,000). Inability to process the amino acid leucine. Can cause coma, brain damage, or death in infancy, or emerge later in childhood after infectious ill-ness....