At a Glance

PKU is a recessively inherited disorder characterized by a deficiency of the liver enzyme phenylalanine hydroxylase. This is necessary for the breakdown of the essential amino acid phenylalanine to tyrosine. As a result of this enzyme deficiency, plasma phenylalanine concentration is elevated and abnormal metabolites are excreted in the urine. This means that in such individuals, normal protein intake produces high levels of toxins, which can lead to mental retardation, seizures and defects in pigmentation.   PKU is treated by a diet low in phenylalanine, which should be introduced immediately after diagnosis.  Evidence suggests that proper dietary management of PKU throughout childhood and into adulthood can lead to normal development.

 

Maple Syrup Urine Disease is an inherited metabolic disorder caused by a deficiency in the body’s ability to properly metabolize the branched-chain amino acids (BCAA) leucine, isoleucine and valine. The disease name originates from the sweet or maple syrup smell of the urine.  Delay in starting treatment may result in severe, sometimes fatal, neurological decline.  Early diagnosis, combined with long term metabolic control is essential in minimizing neurological impairment and poor intellectual development. Leucine is considered to be the most toxic of the BCAA's and it is present in food in greater concentration than isoleucine or valine. The diet is therefore based on restriction of the leucine intake.

 

Homocystinuria is an inherited metabolism disorder of the amino acid methionine, resulting in elevated plasma concentration of both methionine and homocysteine.  Symptoms of HCU include, but are not limited to displacement of the lens of the eye, nearsightedness, and the formation of blood clots in the arteries and veins.  Treatment approaches aimed at lowering total homocysteine may include drug or dietary interventions, or a combination of both. Dietary treatment involves lifetime compliance of a methionine restricted, cystine enriched diet in those individuals who are non responsive or only partially responsive to pyridoxine (vitamin B6) therapy.

 

Tyrosinaemia types I, II and III are rare metabolic disorders caused by enzyme deficiencies involving the breakdown of the amino acid tyrosine.  Tyrosinaemia type I is the most severe, and if untreated can lead to progressive liver failure, renal tubular dysfunction and risk of hepatocellular carcinoma (tumor of the liver). Clinical symptoms of Tyrosinaemia type II are skin and eye abnormalities, while neurological abnormalities have been reported in type III.  Successful treatment is possible with dietary tyrosine and phenylalanine restrictions in all three conditions.

 

MMA and PA are inherited disorders in which the body is unable to process certain proteins, including methionine, threonine, isoleucine, and valine properly, as well as certain fatty acids from foods.  Symptoms such as fatigue, drowsiness vomiting and dehydration typically appear in early infancy.  If left untreated, long – term consequences of MMA and PA can result in mental retardation.  Dietary management involves a food plan that is low in protein and limited in the amino acids methionine, threonine, isoleucine, and valine.

 

For further, detailed information regarding all of the above disorders please, visit the following web pages on Vitaflo International’s website: