What are the Symptoms of Phenylketonuria?


or PKU, is a genetic condition in which a baby is born without an enzyme namely, Phenylalanine Hydroxylase (PAH), which breaks down the amino acid Phenylalanine to amino acid tyrosine. Amino acids are the building blocks of proteins. It is a very rare metabolic disorder which can even lead to mental retardation. About 1 in 10,000 to 15,000 new born are diagnosed with this condition in the US.

What are the symptoms of Phenylketonuria?

Symptoms of PKU generally develop within a few months after being born. The phenylalanine built up in the babyai??i??s system from the protein in the breast milk starts showing symptoms. Inside the womb, this condition is not reflected because the mothers system gets rid of the excess amino acid from the baby. Symptoms are worse when phenylalanine builds up in the brain tissue and affects brain functions and the central nervous system.
The disease in its most severe form is referred to as the

Classic PKU

. The symptoms are discussed below:

  • Neurological impairment, seizures, developmental delays, mental retardation to name a few of the symptoms seen in young children.
  • Vomiting, Diarrhea leading causing weight loss.
  • Irritability and restlessness.
  • Skin problems like itchy skin, dry skin, skin rashes like eczema.
  • The disorder inhibits melanin production which gives color to the skin and hair.This condition is also known as Albinism. These children are comparatively lighter than their healthier siblings.
  • A musty odor in skin, sweat, hair and urine due to accumulation of the amino acid.
  • Delayed social skills.
  • Learning disability and loss of already acquired skills.
  • Smaller head size when compared to normal children around the same age.
  • Among a little older children like those above 8 weeks of age hyperactivity, uncontrollable restlessness, facial tics, extreme rocking, screaming etc are noticed.

A less severe form of the disease called

Variant PKU


non-PKU Hyperphenylalaninemia

has milder symptoms. The mental damage is less and can be reversed with a low-phenylalanine diet.

Babies born to women with phenylketonuria have a higher risk of inheriting it. They are exposed to high levels of phenylalanine before birth and show signs of mental disability later on. Women with this condition often are prone to miscarriages. They generally give birth to babies who are significantly underweight and have developmental delays.

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