Citrullinemia type I is a disease in which ammonia and other toxic substances build up in the blood, causing life-threatening complications shortly after birth.
While infants with citrullinemia type I appear normal at birth, within the first week of life, most will become lethargic and display poor feeding, vomiting, and seizures that often lead to unconsciousness, stroke, increased pressure around the brain, and death if untreated.
While there are less severe and later-onset versions of citrullinemia type I, the mutations for which Counsyl screens are associated with the more severe form that affects infants shortly after birth. It is also known as "classic" citrullinemia.
Citrullinemia type I belongs to a group of diseases known as urea cycle disorders. When the body consumes protein, it also produces excess nitrogen. Under normal circumstances, the body converts that nitrogen to urea, which is then excreted in urine. People with citrullinemia type I are deficient in an enzyme known as argininosuccinate synthase which is needed for this vital process, leading to a buildup of ammonia and other urea cycle byproducts in the body. The excess of ammonia is harmful to the nervous system, causing many of the disease's symptoms.
Scientists estimate that 1 in 57,000 births are affected by Citrullinemia type I.
The goals of treatment for citrullinemia type I are to regulate the amount of ammonia in the blood. Physicians adhere to certain protocols to control the body's ammonia levels. These protocols utilize medication, dialysis, and a specifically prescribed diet. Children with citrullinemia will need to be monitored closely by a physician specializing in metabolic disorders. Physicians will also monitor and attempt to relieve any excess of pressure around the brain.
The prognosis for a child with citrullinemia type I has not been well established. Without treatment, the longest known survival was 17 days. With treatment, these children can survive for an unknown period of time, however they will have significant mental and neurological impairment.
Explanations of an extensive number of genetic diseases written by the U.S. government's National Institutes of Health. Please note this entry covers several forms of citrullinemia.