0 Phenylketonuria



Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional.

The Guthrie test, also known as the Guthrie bacterial inhibition assay, is a medical dried blood spot screening test performed by heel prick on newborn infants to detect various conditions like
  • phenylketonuria ,
  • congenital hypothyroidism, 
  • sickle-cell disease, 
  • cystic fibrosis and 
  • Medium Chain Acyl CoA Dehydrogenase Deficiency (MCADD).

In recent years it is gradually being replaced in many areas by newer techniques such as tandem mass spectrometry (TMS)

Neonatal screening - TMS

Features of PKU
  • Mental Retardation
  • Seizures
  • Musty / Mousy odor to Sweat and Urine (because of phenylacetate)

Treatment -
  • Tyrosine Supplementation 
  • Phenylalanine Restriction (Aim in serum < 6 mg/dl )
  • Important - DO NOT completely stop phenylalanine

Q. Non essential Amino Acid that becomes essential in PKU is ?

ANSWER:
Tyrosine




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