Arginase Deficiency (ARG)

Definition of Arginase Deficiency

Arginase Deficiency (ARG) is inherited as an autosomal recessive genetic disorder and is caused by mutations in the ARG1 gene. Mutations in the ARG1 gene result in production of an abnormal arginase enzyme. The lack of the arginase enzyme results in excessive accumulation of nitrogen, in the form of ammonia (hyperammonemia), in the blood and arginine (hyperarginemia) in the blood and cerebrospinal fluid.


The condition is diagnosed during newborn screening via the heel prick test taken 48-72 hours after birth. Diagnosis can also be made when symptoms present.


1:300,000 to 1,000,000 estimated worldwide.

Arginase Deficiency Treatment

Treatment is based on reducing plasma ammonia and arginine concentration, preventing excess ammonia from being formed, and reducing the amount of nitrogen in the diet. Dietary restrictions in individuals with ARG are aimed at limiting the amount of arginine and protein intake. Children with ARG are placed on a low-protein, arginine-restricted diet supplemented by essential amino acids.

Support Links & Materials

Urea Cycle Disorders Handbook

UCD Fruit and Veg Counting Lists

UCD General Protein Counting Lists