Arginase deficiency is a progressive neurological disorder characterized by episodic hyperammonemia crises. Our patient had been diagnosed with cerebral palsy (spastic paraplegia) in childhood and received rehabilitation. She had suffered parotid swelling since the age of 5 years, prior to liver dysfunction becoming apparent, and then developed hyperamylasemia at 8 years of age. At age 25 years, she presented with hyperammonemia and elevations of aspartate aminotransferase and alanine aminotransferase. At age 27 years, she was diagnosed with arginase deficiency due to hyperargininemia and absent arginase activity in erythrocytes. Liver cirrhosis was also present. She was hospitalized several times for management of episodic hyperammonemia due to recurrent viral infections, an unbalanced diet, and poor compliance with medications.