Organic acidemia is a term used to classify a group of metabolic disorders which disrupt normal amino acid metabolism, particularly branched-chain amino acids, causing a buildup of acids which are usually not present. The branched-chain amino acids include isoleucine, leucine and valine. Organic acids refer to the amino acids and certain odd-chained fatty acids which are affected by these disorders. The four main types of organic acidemia are: methylmalonic acidemia, propionic acidemia, isovaleric acidemia, and maple syrup urine disease..