Developmental Monitoring for Children With Phenylketonuria

Developmental Monitoring for Children With Phenylketonuria

Children with phenylketonuria (PKU) are typically put on a phenylalanine-restricted diet that is low in natural protein. Because the diet can impede normal development, the children require monitoring to ensure that they are otherwise healthy.

What is PKU?

PKU is a metabolic disorder characterized by increased levels of phenylalanine, an amino acid obtained through diet. (Amino acids are the building blocks of proteins.) Phenylalanine is present in all proteins and in some non-protein foods, such as soda drinks and artificial sweeteners.

Diet and physical development

A phenylalanine-restricted diet can help to prevent complications caused by PKU. However, research has shown that such a diet can impede normal development, with patients tending to be overweight and short in stature.

Studies vary as to the degree a low-protein diet directly affects growth. In general, though, infants with PKU tend to have a lower birth weight and grow more slowly than other children.

Developmental monitoring

If your child was diagnosed with PKU at birth, your physician probably talked to you about the likelihood of developmental challenges and the need for monitoring.

In general, developmental monitoring observes how your child grows and changes over time, and whether he or she meets the typical developmental milestones in playing, learning, speaking, moving, and behaving.

PKU study of patient height

A study of 224 PKU patients that appeared in the journal Pediatrics, in November 2017, found that from birth to adulthood, children with PKU were significantly shorter than those without the disease. The patients were diagnosed, treated, and continuously monitored from birth. In the last two decades, however, the growth gap has narrowed between children with PKU and typically developing children, likely due to the use of nutritional supplementation and the growing selection of special low-protein foods for PKU patients.

So far, no conclusive data are available on longitudinal growth, growth rate, or target height for people with PKU. Future extended studies are needed that will investigate the potential role of other factors — including tyrosine, an essential amino acid in the diet, and genetic makeup — in the physical development of PKU patients.


Last updated: June 11, 2020


Phenylketonuria News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

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