Citrullinemia type I

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Citrullinemia type I
Synonyms	Classic citrullinemia, argininosuccinate synthetase deficiency
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Specialty	Medical genetics
Symptoms	Hyperammonemia, lethargy, vomiting, seizures, coma
Complications	N/A
Onset	Neonatal
Duration	Lifelong
Types	N/A
Causes	Mutations in the ASS1 gene
Risks	Family history of the condition
Diagnosis	Genetic testing, ammonia levels, liver function tests
Differential diagnosis	Urea cycle disorders, organic acidemias
Prevention	Genetic counseling
Treatment	Low-protein diet, ammonia scavengers, arginine supplementation
Medication	Sodium phenylbutyrate, sodium benzoate
Prognosis	Variable, depends on early diagnosis and treatment
Frequency	1 in 57,000 to 1 in 250,000 live births
Deaths	Can be fatal if untreated

Citrullinemia Type I

Diagram of autosomal recessive inheritance pattern

Citrullinemia Type I is a rare genetic disorder that affects the urea cycle, a series of biochemical reactions that occur in the liver. This cycle is responsible for removing ammonia from the bloodstream. Ammonia is a waste product of protein metabolism and is toxic if it accumulates in the body.

Pathophysiology

Citrullinemia Type I is caused by a deficiency of the enzyme argininosuccinate synthetase (ASS), which is crucial in the conversion of citrulline and aspartate into argininosuccinate. This enzyme deficiency leads to the accumulation of ammonia and other toxic substances in the blood, resulting in hyperammonemia.

Genetics

Citrullinemia Type I is inherited in an autosomal recessive pattern, which means that both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Clinical Presentation

Symptoms of Citrullinemia Type I usually appear in the first few days of life and can include lethargy, poor feeding, vomiting, seizures, and loss of consciousness. If untreated, the condition can lead to severe brain damage and is potentially life-threatening.

Diagnosis

Diagnosis of Citrullinemia Type I is based on clinical symptoms, biochemical tests showing elevated levels of ammonia and citrulline in the blood, and genetic testing to identify mutations in the ASS1 gene.

Treatment

Management of Citrullinemia Type I involves dietary restrictions to limit ammonia production, medications to remove excess ammonia, and in some cases, liver transplantation. Early diagnosis and treatment are crucial to prevent serious complications.

See also

• Urea cycle disorder
• Hyperammonemia
• Genetic disorder