What causes inherited metabolic disorders?

As the name suggests, inherited metabolic disorders are genetic. In order for the body to break down compounds in food like carbohydrates, proteins, or fats, it needs certain chemical substances called enzymes. However, in some cases, a genetic abnormality causes certain enzymes to function abnormally or to be missing altogether. As substances that should be broken down build up, or as the body fails to make a substance it needs to function properly, a metabolic disorder develops.