Citrullinemia Type I
Description
Citrullinemia Type I is a rare, inherited metabolic disorder affecting the body‘s ability to break down ammonia, a toxic byproduct of protein breakdown. This leads to an accumulation of ammonia in the blood, causing various health problems. While there‘s no cure, early diagnosis and management are crucial for individuals with Citrullinemia Type I to thrive.
Genes Involved
Citrullinemia Type I is caused by mutations in the ASS1 gene, located on chromosome 9. This gene provides instructions for making argininosuccinate synthetase, an enzyme vital for ammonia detoxification.
Recognizing the Signs and Symptoms
Symptoms of Citrullinemia Type I can vary in severity and often appear within the first few days or weeks of life. Common signs include:
- Lethargy: A general lack of energy and sluggishness.
- Poor feeding: Difficulty sucking, swallowing, or gaining weight.
- Vomiting: Frequent or forceful vomiting.
- Irritability: Fussiness and crying more than usual.
- Seizures: Episodes of uncontrolled muscle movements.
- Respiratory problems: Difficulty breathing.
- Delayed development: Slowed growth and cognitive development.
- Enlarged liver: The liver may be noticeably bigger than normal.
- Jaundice: Yellowing of the skin and whites of the eyes.
- Coma: A state of unconsciousness.
Causes
Citrullinemia Type I is an inherited disorder, meaning it is passed down through families. Parents who carry the mutated ASS1 gene have a 50% chance of passing it on to their children. If a child inherits the mutated gene from both parents, they will develop the disorder.
Inheritance/recurrence risk
Citrullinemia Type I is inherited in an autosomal recessive pattern. This means that an individual must inherit two copies of the mutated ASS1 gene, one from each parent, to develop the disorder. If both parents carry the mutated gene, there is a 25% chance for each child to inherit two copies (and have the disorder), a 50% chance to inherit one copy (and be a carrier), and a 25% chance to inherit two normal copies (and not have the disorder).
