Propionic acidemia is a rare genetic disease characterized by incomplete metabolism of certain amino acids and, to a lesser degree, fats and cholesterol. The processing error causes propionic acid and other toxic substances to accumulate in the blood. Left untreated, these toxins damage the body’s organs especially the brain.
Propionic acidemia varies in severity. Some individuals show only mild symptoms, while in others life-threatening complications such as stroke and coma occur. Progressive brain damage is a characteristic feature.
The amino acids that cause a problem in propionic acidemia are isoleucine, valine, threonine and methionine. Amino acids are the building blocks of proteins. After eating proteins, the body ‘metabolizes’ or breaks them down into amino acids. Animal proteins include dairy products, meat, eggs and fish. Proteins are also found in plants including soy, legumes, grains and nuts. The body uses the amino acids to make its own proteins essential for life – for example enzymes; structural proteins in muscles, hair, skin, cells and cartilage; proteins that generate movement in muscles; or those involved in cell functioning or immune responses. In periods of fasting or illness, the body often switches to use its own proteins, and stored fats, to generate energy. Leucine, isoleucine, valine and threonine are essential amino acids meaning that the body cannot make them. Therefore, these amino acids come from ingested protein or from the breakdown of previously ingested and stored proteins.