Genetic disease of the metabolism of urea

The genetic diseases of the metabolism of the urea include/understand the diseases in connection with an anomaly of the metabolism of the urea by defect of the enzymatic operation of one of the Enzyme S secondary with a defect of the Gène coding the Enzyme impliqué.
The Cycle of the urea is the metabolic way by which the Ammoniaque is transformed into Urée.
the faulty operations of the first four enzymes lead to the accmulation of ammonia and its metabolites during the first days of life and appear neurological signs quickly.

Prevalence

The Prévalence of this pathology is estimated at one on 30000 births

Description

The enzymes impliquès in the metabolism of urea are, in the order of their intervention:
  • Carbamyl-phosphate synthétase
  • Ornithin carbamyl transférase
  • N-Acétylglutamate synthase
  • Arginosuccinase
  • Arginase
  • Cofacteur: N-acetyl glutamate synthetase
The clinques demonstrations of the deficit enzymatic of the cycle of urea are common for all the enzymes except the deficit in arginase. The clinical demonstrations of these diseases occur are is:

Demonstrations néonatales

  • In connection with a total enzymatic deficit
  • intracranial Signs hypertension with lethargy, hyper or hypoventilation, hypothermia, convulsion and coma.
  • These signs appear immediately after the birth or with the re-entry at the house and intracranial hypertension beginner appears by a loss of appetite with hypothermia and somnolence
Demonstrations during childhood
  • If the enzymatic deficit is partial, the signs of hyperammoniemy appears only in the event of stress or of disease
Manifestations at the adulthood
  • the signs is sometimes benign in connection with a tiny deficit and the patient complains about loss about appetite, cyclic vomiting or abnormal behavior.

  • the deficit in arginase pricipalement appears by neurological signs

Diagnosis

The diagnosis rests on the genetic private clinic, biology and data:
  • a plasmatic ammonia concentration higher than 150 millimole per liter with normal glycemia associated with an absence of anion Trou is very evocative of a disorder of the metabolism of urea.

Various diseases

Sources

  • French Site on the rare diseases
  • GeneTests: Medical Genetics Information Resource (database online). Copyright, University off Washington, Seattle. 1993-2005 * Online Mendelian Inheritance in Man, OMIM (TM). Johns Hopkins University, Baltimore, MANDELEVIUM.

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