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A urea cycle disorder is a genetic disorder caused by a deficiency of one of the enzymes in the urea cycle which is responsible for removing ammonia from the blood stream. 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. Normally, the urea is transferred into the urine and removed from the body. In urea cycle disorders, the nitrogen accumulates in the form of ammonia, a highly toxic substance, and is not removed from the body. Ammonia then reaches the brain through the blood, where it causes irreversible brain damage and/or death.
Urea cycle disorders are included in the category of inborn errors of metabolism. There is no cure. Inborn errors of metabolism are generally considered to be rare but represent a substantial cause of brain damage and death among newborns and infants. Because many cases of urea cycle disorders remain undiagnosed and/or infants born with the disorders die without a definitive diagnosis, the exact incidence of these cases is unknown and underestimated. It is believed that up to 20% of Sudden Infant Death Syndrome cases may be attributed to an undiagnosed inborn error of metabolism such a urea cycle disorder. In April 2000, research experts at the Urea Cycle Consensus Conference estimated the incidence of the disorders at 1 in 10000 births. This represents a significant increase in case diagnosis in the last two years.
Children with severe urea cycle disorders typically show symptoms after the first 24 hours of life. The baby may be irritable at first, followed by vomiting and increasing lethargy. Soon after, seizureThis article is about the medical condition. In law, seizure can also refer to taking possession of an item: see search and seizure. Seizures (or convulsions are temporary alterations in brain functions due to abnormal electrical activity of a group of brs, hypotoniaHypotonia is abnormally decreased muscle tone. Those who suffer from hypotonia are often described as feeling and appearing as though they are "rag dolls" and are unable to bend their ligaments while they are able to extend them beyond normal lengths. (poor muscle tone), respiratory distress, and coma may occur. If untreated, the child will die. These symptoms are caused by rising ammonia levels in the blood. Acute neonatal symptoms are most frequently seen in, but not limited to, boys with OTC Deficiency.
Children with mild or moderate urea cycle enzyme deficiencies may not show symptoms until early childhood. Early symptoms may include hyperactive behavior, sometimes accompanied by screaming and self-injurious behavior, and refusal to eat meatMeat is animal flesh (mainly muscle tissue) used as food, sometimes with the exception of fish, other seafood, and poultry. Originally, the word meat meant simply "food". It is also used as a vulgar way to refer to the human body. see meat market. For the or other high-protein foods. Later symptoms may include frequent episodes of vomiting, especially following high-protein meals; lethargy and deliriumDelirium is a medical term used to describe a mental state. There are several definitions (including those in the DSM-IV and ICD-10). However, all include some core features. These include: impairments of consciousness confusion and disorientation cogniti; and finally, if the condition is undiagnosed and untreated, coma and death. Children with this disorder may be referred to child psychologists because of their behavior and eating problems. Childhood episodes of hyperammonemia (high ammonia levels in the blood) may be brought on by viral illnesses including chicken pox, high-protein meals, or even exhaustion. The condition is sometimes misdiagnosed as Reye’s Syndrome . Childhood onset can be seen in both boys and girls.