Citrullinemia Type 1 (ASS1)
| Disorder | Citrullinemia, Type 1 | |
| Gene Name | ASS1 | |
| Clinical info | Citrullinemia type I is an inborn error of amino acid metabolism caused by the deficiency of argininiosuccinate synthase (ASS1), which performs the third enzymatic step in the urea cycle, condensing citrulline and aspartic acid to form argininosuccinic acid. Patients are often identified by newborn screening, due to an accumulation of citrulline in the blood. Citrullinemia type I exhibits a broad clinical spectrum. Most patients present with a severe neonatal form characterized by hyperammonemia, vomiting, lethargy, failure to thrive, seizures, spasticity and increased intracranial pressure. Patients typically progress quickly to a coma and the disorder is fatal unless treated promptly. Other patients may exhibit a milder later-onset form of the disorder, and others appear to be asymptomatic. | |
| Indications | Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis. | |
| Associated Tests | Plasma amino acids | |
| Detection | ASS1 sequencing will detect mutations in approximately 96% of alleles in patients with citrullinemia type I. | |
| Specimen Requirements | 5 to 10 ml of peripheral blood collected in an EDTA (lavender top) Vacutainer tube is preferred. The minimal blood needed for reliable DNA isolation is 3 ml | |
| Transport | The specimen should be kept at room temperature and delivered via overnight shipping. FedEx is preferred. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery. | |
| Turnaround time | 14 days | |
| Prenatal testing | Prenatal diagnosis is available if the familial mutations are known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen. | |
| CPT Codes | Unknown mutation 81479 Known mutation 81479 |
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| Cost | $1800 for sequencing $350 for known mutation |
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| Contact | For further information contact This email address is being protected from spambots. You need JavaScript enabled to view it. , MS, Lab Counselor at 1-800-473-9411. | |
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Kellie King, MS, CGC
Molecular Diagnostic Lab
The Molecular Diagnostic Lab offers DNA analysis for many genetic disorders via gene sequencing, targeted mutation analysis, MLPA deletion/duplication testing, trinucleotide repeat analysis and next generation sequencing panels.