Question

I recently noticed that my baby is always in a poor state of mind, often distracted, and has very little hair. I suspect he might have phenylketonuria. Could you tell me what are the typical symptoms of phenylketonuria?

Answer

Generally, infants with phenylketonuria appear normal at birth, but symptoms may start to reappear between 3 to 6 months old. Particularly, symptoms become apparent around 1 year old, primarily manifesting as delayed cognitive and behavioral development in the nervous system, along with hyperactivity or severe muscle pain, epilepsy-like minor seizures. In rare cases, increased muscle tone and exaggerated reflexes may occur. BH4-deficient PKU infants may experience earlier and more severe nervous system symptoms. Common symptoms include decreased muscle tone, anorexia, and seizures. In infants with more obvious physical symptoms, hair, skin, and iris color may lighten due to insufficient melanin production within a few months after birth. Dry heaves and skin eczema are also very common.