Urea Cycle Disorders (UCD)
UCDs are caused by a deficiency of one of the enzymes in the urea cycle, which is responsible for the removal of ammonia, a potent neurotoxin, from the body. The urea cycle involves a series of biochemical steps in which nitrogen, a waste product of protein metabolism, is removed from the blood and converted to urea, which is excreted in the urine. In UCDs, the nitrogen removal is blocked and it accumulates in the form of ammonia. Left untreated, UCDs can cause dangerously increased levels of ammonia in the bloodstream (hyperammonemia) resulting in brain damage, coma and, if untreated, death.