Argininemia

Signs and symptoms

The presentation of argininemia, in those that are affected, is consistent with the following:

• Lethargy
• Dehydration
• Hypotonia
• Stunted growth
• Microcephaly
• Seizures

Genetics

Mutations in the ARG1 gene cause argininemia, which belongs to a class of genetic diseases called urea cycle disorders. The urea cycle is a sequence of reactions that occurs in liver cells (hepatocytes). This cycle processes excess nitrogen, generated when protein is used by the body, making urea that is excreted via the kidneys.

The ARG1 gene provides instructions for making an enzyme called arginase, this enzyme controls the last steps of the urea cycle, which produces urea by extracting nitrogen from arginine. In people with arginase deficiency, arginase is missing, and arginine is not broken down properly. consequently, urea cannot be produced and excess nitrogen accumulates in the blood in the form of ammonia. Ammonia and arginine are thought to cause neurological problems and other symptoms of arginase deficiency.

This condition is an autosomal recessive disorder, which means the defective gene is located on an autosome, and two copies of the defective gene are required to inherit the disorder.

Both parents of an individual with an autosomal recessive disorder are carriers of one copy of the gene, but usually do not have the disorder.

Diagnosis

The diagnosis for argininemia can usually be done using fetal blood sample. One can look for the following indicators as to the presence of the condition:

• Plasma ammonia concentration.
• Urinary orotic acid concentration
• Red blood cell arginase enzyme activity (measurement)

Treatment

The treatment for people with argininemia includes:

• Sodium benzoate
• Sodium phenylbutyrate
• Carglumic acid
• Glycerol phenylbutyrate
• Palonosetron
• Ondansetron hydrochloride

Pegzilarginase (Loargys) was approved for medical use in the European Union in December 2023.

References

References

1. {{OMIM. 207800
2. (1 January 1993). "Arginase Deficiency". GeneReviews.
3. "Arginase deficiency". [[National Library of Medicine]].
4. (15 April 2016). "Arginase Deficiency: Background, Pathophysiology, Epidemiology".
5. "ARG1 gene".
6. (1 January 1993). "Urea Cycle Disorders Overview". GeneReviews.
7. (2005). "Instant Notes in Biochemistry.". Taylor & Francis Ltd..
8. (2015). "Pediatric Gastrointestinal and Liver Disease". Elsevier Health Sciences.
9. (18 December 2023). "Loargys Product information".