Diseases

Phenylketonuria

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An inherited metabolic disorder caused by an enzyme deficiency resulting in accumulation of phenylalanine and its metabolites in the blood causing usually severe mental retardation and seizures unless phenylalanine is restricted from the diet beginning at birth —abbreviation pku

SYMPTOMS

Newborns with pku initially don't have any symptoms. However, without treatment, babies usually develop signs of pku within a few months.

Pku signs and symptoms can be mild or severe and may include:

a musty odor in the breath, skin or urine, caused by too much phenylalanine in the body
neurological problems that may include seizures
skin rashes (eczema)
fair skin and blue eyes, because phenylalanine can't transform into melanin — the pigment responsible for hair and skin tone
abnormally small head (microcephaly)
hyperactivity
intellectual disability
delayed development
behavioral, emotional and social problems
psychiatric disorders

CAUSES

Autosomal recessive inheritance pattern

A defective gene (genetic mutation) causes pku, which can be mild, moderate or severe. In a person with pku, this defective gene causes a lack of or deficiency of the enzyme that's needed to process phenylalanine, an amino acid.
A dangerous buildup of phenylalanine can develop when a person with pku eats protein-rich foods, such as milk, cheese, nuts or meat, and even grains such as bread and pasta, or eats aspartame, an artificial sweetener. This buildup of phenylalanine results in damage to nerve cells in the brain.