Phenylketonuria PKU

• Facts:
  Autosomal recessive condition, where there is a deficiency in phenylalanine hydroxylase (breaks down phenylalanine into tyrosine), leading to accumulation of phenylalanine
  
  Patients appear normal at birth, but manifest characteristic features during infancy
  
• History / PE:
  Urine has musty odor (from phenylacetic acid)
  Fair skin, blue eyes, eczema
• Diagnosis:
  Elevated phenylalanine blood levels ( > 20mg/dL)
  Guthrie test (qualitative, coloration test)
  Normal tetrahydrobiopterin (confirm diagnosis)
• Treatment:
  Low phenylalanine diet
  Avoid high protein foods
  
• Complications:
  Mental retardation
  Seizures
• Notes:
  Guthrie test detects the metabolic products of phenylalanine in the urine
• Differential Diagnosis:
  1) Benign hyperphenylalaninemia (mildly elevated phenylalanine)
  2) Transient hyperphenylalaninemia (asymptomatic)
  3) Tyrosinemia (babys smell like boiled cabbage)
  4) Alkaptonuria (homogentisic acid in urine)