Phenylketonuria is an inborn error of metabolism resulting from a deficiency of phenylalanine hydroxylase that is responsible for processing the essential amino acid phenylalanine and leads to elevated levels of phenylalanine and phenylalanine metabolites. PKU is inherited as an autosomal recessive trait. The mutation that causes PKU is located on chromosome 12. The specific type of mutation varies, resulting in variable severity in the clinical course of the disorder.

Newborn screening is very important for the diagnosis of this disease and has largely eliminated mental retardation caused by this disease.

SYMPTOMS :

Symptoms in newborn

• Symptoms are usually absent
  
  
• May be abnormally drowsy or listless
  
  
• Feeding difficulty
  
  
• Light hair, skin and eyes
  
  
• Eczema
  
  
• Severe mental retardation if not treated
  
  
  

Symptoms in children

• Seizures
  
  
• Nausea
  
  
• Vomiting
  
  
• Hyperactivity
  
  
• Aggressive behavior
  
  
• ClumsyPoor coordination
  
  
• Abnormal gait
  
  
• Abnormal posturing
  
  
• Self-injurious behavior
  
  
• Mousy body odor
  
  

PKU in the mother and pregnancy:

Elevated levels of phenylalanine in the mother during pregnancy are teratogenic. It can result into

• Spontaneous miscarriage
  
  
• IUGR
  
  
• Microcephaly
  
  
• Psychomotor retardation
  
  
• Congenital heart defects
  
  
• Postnatal growth retardation
  
  
• Abnormal neurological findings
  
  
• Mild craniofacial dysmorphic features
  
  

Higher the levels of phenylalanine in the mother, greater are the adverse effects seen in the developing fetus. Also the abnormalities are more likely to occur if there is no control of phenylalanine levels during the period of embryogenesis and organogenesis in pregnancy.