Ornithine transcarbamylase (OTC) deficiency

A rare metabolic disorder, OTC is one of the urea-cycle disorders.

The urea cycle is a series of five liver enzymes that help rid the body of ammonia, a toxic breakdown product of protein.

When one of these enzymes is missing or deficient, ammonia accumulates in the blood and travels to the brain, causing coma, brain damage and death.</P> OTC deficiency is the most common of the urea-cycle disorders, occurring in one out of every 40,000 births.

The genetic mutation responsible for OTC occurs on the X chromosome, so women are typically carriers, while their sons with the gene suffer the disease.</P> Severe OTC deficiency is a devastating disease.

Typically, newborns slip into a coma within 72 hours of birth.

Most suffer severe brain damage.

Half die in the first month, and half of the survivors die by age 5.</P> Treatment includes a low-protein formula called keto-acid and sodium benzoate, a preservative, and another type of sodium, which binds to ammonia and helps eliminate it from the body.