Sometimes urea is not processed properly within the body, often a sign of a urea cycle disorder. The condition is genetically inherited and is caused by a deficiency of one of the enzymes that is supposed to remove the waste product nitrogen, generated by protein metabolism, from the blood. The nitrogen accumulates in people with urea cycle disorders and is stored as ammonia, rather than being transferred into urea and exiting the body with the urine. Extremely toxic, the substance migrates through the blood into the brain where it can cause severe damage and even death.