Phenylketonuria (PKU)

What Is It?

Phenylketonuria (PKU) is a rare genetic (inherited) disorder that can cause abnormal mental and physical development if not detected promptly and treated appropriately.

Normally, when a person eats foods that contain protein, special chemicals called enzymes break down these proteins into amino acids. The amino acids are then broken down further by other enzymes. A person with PKU does not have enough of the specific enzyme that breaks down the amino acid phenylalanine. Therefore, any phenylalanine in the food someone eats cannot be digested properly and collects in the body.

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