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Items: 6

1.

Urea

end product of bodily protein consumption [from CHV]

MedGen UID:
21773
Concept ID:
C0041942
Biologically Active Substance; Organic Chemical; Pharmacologic Substance
2.

Disorder of the urea cycle metabolism

The urea cycle disorders (UCD) result from defects in the metabolism of waste nitrogen from the breakdown of protein and other nitrogen-containing molecules. Severe deficiency or total absence of activity of any of the first four enzymes (CPS1, OTC, ASS, ASL) in the urea cycle or the cofactor producer (NAGS) results in the accumulation of ammonia and other precursor metabolites during the first few days of life. Infants with a severe urea cycle disorder are normal at birth but rapidly develop cerebral edema and the related signs of lethargy, anorexia, hyper- or hypoventilation, hypothermia, seizures, neurologic posturing, and coma. In milder (or partial) deficiencies of these enzymes and in arginase (ARG) deficiency, ammonia accumulation may be triggered by illness or stress at almost any time of life. In these disorders the elevations of plasma ammonia concentration and symptoms are often subtle and the first recognized clinical episode may not occur for months or decades. [from GeneReviews]

MedGen UID:
57586
Concept ID:
C0154246
Disease or Syndrome
3.

Argininosuccinate lyase deficiency

Deficiency of argininosuccinate lyase (ASL), the enzyme that cleaves argininosuccinic acid to produce arginine and fumarate in the fourth step of the urea cycle, is characterized by a severe neonatal onset form and a late onset form. The severe neonatal onset form, which is indistinguishable from that of other urea cycle disorders, is characterized by hyperammonemia within the first few days after birth accompanied by vomiting, lethargy, hypothermia, and poor feeding. In the absence of treatment, lethargy, seizures, and coma worsen, resulting in death. In contrast, the late onset form ranges from episodic hyperammonemia triggered by acute infection or stress to cognitive impairment, behavioral abnormalities, and/or learning disabilities in the absence of any documented episodes of hyperammonemia. Manifestations of ASL deficiency that appear to be unrelated to the severity or duration of hyperammonemic episodes include: (1) neurocognitive deficiencies (attention deficit hyperactivity disorder [ADHD], developmental disability, seizures, and learning disability); (2) liver disease (hepatitis, cirrhosis); (3) trichorrhexis nodosa (coarse brittle hair that breaks easily); and (4) systemic hypertension. [from GeneReviews]

MedGen UID:
78687
Concept ID:
C0268547
Disease or Syndrome
4.

Carbamoyl-phosphate synthetase 1 deficiency

Carbamoyl-phosphate synthetase 1 deficiency (CPS1D) is a rare and severe disorder of urea cycle metabolism most commonly characterized by either a neonatal-onset of severe hyperammonemia that occurs few days after birth and manifests with lethargy, vomiting, hypothermia, seizures, coma and death or a presentation outside the newborn period at any age with (sometimes) milder symptoms of hyperammonemia. [from ORDO]

MedGen UID:
910929
Concept ID:
CN199561
Finding
5.

Citrullinemia type I

Citrullinemia type I is a rare autosomal recessive urea cycle defect characterized biologically by hyperammonemia and clinically by progressive lethargy, poor feeding and vomiting in the neonatal form (Acute neonatal citrullinemia type I, see this term) and by variable hyperammonemia in the later-onset form (Adult-onset citrullinemia type I, see this term). [from ORDO]

MedGen UID:
831929
Concept ID:
CN201792
Disease or Syndrome
6.

Citrullinemia type I

Citrullinemia type I (CTLN1) presents as a clinical spectrum that includes an acute neonatal form (the "classic" form), a milder late-onset form (the “non-classic” form), a form without symptoms or hyperammonemia, and a form in which women have onset of severe symptoms during pregnancy or post partum. Distinction between the clinical forms is based on clinical findings and is not clear-cut. Infants with the acute neonatal form appear normal at birth. Shortly thereafter, they develop hyperammonemia and become progressively lethargic, feed poorly, often vomit, and may develop signs of increased intracranial pressure (ICP). Without prompt intervention, hyperammonemia and the accumulation of other toxic metabolites (e.g., glutamine) result in increased ICP, increased neuromuscular tone, spasticity, ankle clonus, seizures, loss of consciousness, and death. Children with the severe form who are treated promptly may survive for an indeterminate period of time, but usually with significant neurologic deficits. The late-onset form may be milder than that seen in the acute neonatal form, for unknown reasons. The episodes of hyperammonemia are similar to those seen in the acute neonatal form, but the initial neurologic findings may be more subtle because of the older age of the affected individuals. [from GeneReviews]

MedGen UID:
104491
Concept ID:
C0175683
Disease or Syndrome
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