Arginase 1 deficiency (ARG1-D) is a rare condition where the body can't break down a chemical called arginine. This results in high arginine levels, leading to health issues. Loargys is a new treatment to help lower arginine by using a modified enzyme that breaks down arginine in the blood. The amount of Loargys given to each patient is adjusted based on their arginine level. To get accurate test results, a special substance, nor-NOHA, is added to blood samples to stop the breakdown of arginine after collection. The study uses the Loargys Arginine Test System, which includes special tubes and a lab test to measure arginine levels. The goal of the study is to ensure this test system is safe for those taking Loargys.

• Participants must be currently treated with Loargys for ARG1-D.
• Participants need to sign a form agreeing to join the study.
• No specific conditions to exclude someone from joining the study.