Home > Encyclopedia of Genetic Disorders > Urea cycle disorders

Definition

Urea cycle disorders are inborn errors in metabolism that can lead to brain damage and death. They involve a deficiency in one of the enzymes required by the urea cycle that removes ammonia from the blood.

Description

Ammonia accumulates in toxic levels if the urea cycle does not convert nitrogen from protein metabolism into urea for excretion into the urine. A series of biochemical reactions are necessary to complete the urea cycle. When an enzyme is missing or deficient, the cycle is interrupted and nitrogen accumulates in the form of ammonia. It cannot be excreted from the body and enters the blood stream, damaging nervous tissues, including the brain.

Seizures, poor muscle tone, respiratory distress, and coma follow if an affected infant is not treated. Acute neonatal...