Gene therapy: a rocky start to the new millennium

Abstract

Ornithine transcarbamylase deficiency is a genetic disorder caused by a deficiency of one of the enzymes in the urea cycle. The urea cycle, which takes place in the liver, removes nitrogen from the blood and converts it to urea, which is then excreted in the urine. Each of the five steps of the urea cycle requires a specific enzyme. When one of these enzymes is missing, nitrogen accumulates and is converted into ammonia instead of urea. Ammonia is toxic – even modest rises in the brain can cause irreversible brain damage and/or death.