Arginase deficiency is part of the urea cycle. What is the recommended dietary treatment?

• A. High-protein diet
• B. Ketogenic diet
• C. Low-protein diet without arginine
• D. Vitamin supplementation

Answer: (C)

Arginase deficiency disrupts the last step of the urea cycle, so arginine cannot be efficiently converted to urea and ornithine. Because the problem is excess nitrogen entering the system and specifically excess arginine, the treatment focuses on limiting any further nitrogen load and reducing arginine intake. A low-protein diet minimizes the amount of nitrogen you introduce with meals, and avoiding arginine-rich foods prevents adding more arginine that cannot be cleared effectively. This approach directly targets the metabolic bottleneck, helping to prevent hyperammonemia and arginine accumulation. In contrast, increasing protein would raise nitrogen load, a ketogenic diet isn’t the standard management for this condition, and vitamin supplementation doesn’t address the specific metabolic defect.