Arginase Deficiency (also called argininemia) is a rare inherited urea cycle disorder in which the body lacks enough of the enzyme arginase. This enzyme normally helps break down the amino acid arginine and remove nitrogen as urea. Because the enzyme does not function properly, arginine builds up in the blood and the body cannot efficiently eliminate nitrogen waste. This can lead to neurological and metabolic symptoms over time.

• Cause: A rare inherited urea cycle disorder caused by mutations in the ARG1 gene, leading to deficient arginase enzyme activity and elevated arginine levels.

• Features: Typically presents in early childhood with progressive lower-limb spasticity, developmental delay, seizures, and possible episodes of hyperammonemia.

• Diagnosis: Identified by elevated plasma arginine on amino acid analysis and confirmed with ARG1 genetic testing.

• Treatment: focuses on controlling arginine and ammonia levels through a protein-restricted diet, essential amino acid supplementation, and ammonia-lowering medications when needed.