The disease presents as a clinical spectrum that includes an acute neonatal form (the "classic" form), a milder late-onset form, and a form in which women have onset of severe symptoms during pregnancy or postpartum. Individuals remaining asymptomatic up to at least age ten have also been reported. Distinction between the clinical forms is based on clinical findings and is not clear-cut. Classic neonatal-onset citrullinemia type I is suspected in infants who have been on a full protein diet and who present in the first week of life with hyperammonemia, lethargy, refusal to feed, and vomiting. Hyperammonemia may lead to increased intracranial pressure, which can cause increased neuromuscular tone, spasticity, ankle clonus, seizures, loss of consciousness, and death. Children with the severe form who are treated promptly may survive for an indeterminate period of time, but usually with significant neurologic deficits. Milder, adult-onset citrullinemia type I is suspected in individuals with recurrent lethargy, somnolence, mental retardation, and chronic or recurrent hyperammonemia. CTLN1 occurs in 1:57,000 births.
Citrullinemia type I is caused by mutations in the ASS1 gene (9q34.1). Sequencing of the ASS1 gene is recommended after a biochemical diagnosis of CTLN1, and provides a complementary method to confirm the presence of mutations in a proband, identify carriers among the proband's relatives, and provide prenatal diagnosis in families with known mutations.
- OMIM #215700: Citrullinemia, Classic
- Confirmation of a clinical/biochemical diagnosis of citrullinemia type I
- Carrier testing in adults with a family history of citrullinemia type I
Analytical Sensitivity: ~99%
Submit only 1 of the following specimen types
Preferred specimen type: Whole Blood
Type: Whole Blood
Specimen Requirements:In EDTA (purple top) or ACD (yellow top) tube:
Infants (<2 years): 2-3 ml
Children (>2 years): 3-5 ml
Older Children & Adults: 5-10 ml
Specimen Collection and Shipping: Refrigerate until time of shipment. Ship sample within 5 days of collection at room temperature with overnight delivery.
Specimen Requirements:OrageneTM Saliva Collection kit (available through EGL) used according to manufacturer instructions.
Specimen Collection and Shipping: Store sample at room temperature. Ship sample within 5 days of collection at room temperature with overnight delivery.