Some produce relatively unimportant physical features or skeletal abnormalities. Others produce serious disease and even death. The gene defect can cause a particular enzyme to be defective or missing. And because the enzyme isn't doing what it is supposed to do for the body, poor health may result. Simply put, enzymes help the body by stimulating biological reactions inside cells.
Enzymes are proteins that help the body use food, produce energy, and do work.
When a particular enzyme is defective or missing, then the body isn't able to do something that it should do to maintain health. The enzyme involved determines what the body can't do and what the resulting physical features are. Inborn errors of metabolism affect about 1 in every 5,000 babies born. The symptoms of inborn errors of metabolism vary greatly. Each one must be reviewed separately to know what the physical features are.