Citrullinemia Workup

Updated: Aug 06, 2019
  • Author: Karl S Roth, MD; Chief Editor: Maria Descartes, MD  more...
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Laboratory Studies

In patients with citrullinemia who are symptomatic, the measurement of blood ammonia levels is the primary laboratory test in diagnosis. No other routinely obtained study provides diagnostically useful information.

Quantitative measurement of blood amino acid levels is the next immediate step. Citrulline levels are unmistakably elevated in patients with citrullinemia. In such patients, urine amino acid, urine organic acid, and urine orotic acid levels should be analyzed. Orotic acid levels in urine are abnormally elevated in citrullinemia.

Measurement of argininosuccinic acid (ASA) synthase in cultured skin fibroblasts can provide an unequivocal biochemical diagnosis.

Molecular analysis of the gene should be pursued to establish the nature of the mutation, which can be used for prenatal diagnostic studies.

In neonates who are jaundiced and have normal or mildly elevated ammonia levels, hypercholesterolemia suggests citrin deficiency. [12, 3]


Imaging Studies

MRI of the brain in affected infants shows several associated abnormalities, the extent of which are helpful in predicting neurological outcomes. [13, 14, 15]


Other Tests

New experimental data in a mouse model have suggested that T-cell function may be impaired in individuals with citrullinemia. [16]