Carbamoyl Phosphate Synthetase Deficiency Clinical Presentation

  • Author: Karl S Roth, MD; Chief Editor: Bruce Buehler, MD   more...
 
Updated: Mar 13, 2012
 

History

In homozygous neonates, early-onset lethargy and, in some cases, seizures are often the first signs of abnormality. Because the fetus is generally anabolic and maternal metabolism can usually manage the additional ammonia load from the fetus, intrauterine development is completely unaffected. Therefore, infants are usually born at term following a completely uneventful pregnancy and delivery.

Ammonia levels begin to rise after the maternal-fetal circulation is interrupted at birth, with a brief period of fasting. The baby becomes irritable, then lethargic, and, if untreated, comatose. Without rapid recognition and aggressive treatment, the infant suffers devastating CNS damage, coma, and death.

Some individuals with carbamoyl phosphate synthetase (CPS) deficiency reach adulthood prior to diagnosis. One known case involved a college-educated homozygous woman whose clinical onset occurred within hours after childbirth and resulted in death.[4]

The multiple primary causes of hyperammonemia, specifically those due to urea cycle enzyme deficiencies, vary in manifestation, diagnostic features, and management. For these reasons, the urea cycle defects are considered individually in this article; however, hyperammonemia is the common denominator and generally manifests clinically as a common constellation of signs and symptoms. As a consequence, the most striking clinical findings of each individual urea cycle disorder relate to this constellation of symptoms and rough temporal sequence of events. Symptoms include the following:

  • Anorexia
  • Irritability
  • Heavy or rapid breathing
  • Lethargy
  • Vomiting
  • Disorientation
  • Somnolence
  • Asterixis (rare)
  • Combativeness
  • Obtundation
  • Coma
  • Cerebral edema
  • Death (if treatment is not forthcoming or effective)
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Physical

General

Signs of severe hyperammonemia may be present (see Hyperammonemia).

Poor growth may be evident.

Head, ears, eyes, nose, and throat (HEENT)

Papilledema may be present if cerebral edema and increased intracranial pressure have occurred.

Pulmonary

  • Tachypnea or hyperpnea may be present.
  • Apnea and respiratory failure may occur in later stages.

Abdominal

Hepatomegaly may be present and is usually mild.

Neurologic

  • Poor coordination
  • Dysdiadochokinesia
  • Hypotonia or hypertonia
  • Ataxia
  • Tremor
  • Seizures and hypothermia
  • Lethargy progressing to combativeness, obtundation, and coma
  • Decorticate or decerebrate posturing
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Causes

CPS I deficiency is autosomal recessive. The structural gene for the enzyme is assigned to chromosome 2 and mapped to band 2q35. It has been sequenced and cloned.

Urea cycle defects with resulting hyperammonemia are due to deficiencies of the enzymes involved in the metabolism of waste nitrogen. The enzyme deficiencies lead to disorders with nearly identical clinical presentations. The exception is arginase, the last enzyme of the cycle; arginase deficiency causes a somewhat different set of signs and symptoms (see Arginase Deficiency).

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Contributor Information and Disclosures
Author

Karl S Roth, MD  Professor and Chair, Department of Pediatrics, Creighton University School of Medicine

Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Clinical Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Robert D Steiner, MD  Credit Unions for Kids Professor of Pediatric Research, Professor of Pediatrics and Molecular and Medical Genetics, Vice Chair for Research, Department of Pediatrics, Faculty, Program in Molecular and Cellular Biosciences, Oregon Health and Science University School of Medicine; Attending Physician, Doernbecher Children's Hospital; Staff Consultant, Director of Metabolic Bone Disease Clinic, Shriners Hospital Portland

Robert D Steiner, MD is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American College of Medical Genetics, American Society of Human Genetics, Oregon Medical Association, Society for Inherited Metabolic Disorders, Society for Pediatric Research, Society for the Study of Inborn Errors of Metabolism, and Western Society for Pediatric Research

Disclosure: Amicus Honoraria Consulting; Actelion Honoraria Consulting; Actelion Honoraria Speaking and teaching; Biomarin Honoraria Consulting; Genzyme Honoraria Consulting; Shire Honoraria Consulting

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Leonard G Feld, MD, PhD, MMM, FAAP  Sara H Bissell and Howard C Bissell Endowed Chair in Pediatrics, Chief Medical Officer, Levine Children's Hospital, Carolinas Medical Center

Leonard G Feld, MD, PhD, MMM, FAAP is a member of the following medical societies: American Academy of Pediatrics, American College of Physician Executives, American Society of Nephrology, American Society of Pediatric Nephrology, International Society of Nephrology, and Juvenile Diabetes Foundation International

Disclosure: Nothing to disclose.

Paul D Petry, DO, FACOP, FAAP  Consulting Staff, Freeman Pediatric Care, Freeman Health System

Paul D Petry, DO, FACOP, FAAP is a member of the following medical societies: American Academy of Osteopathy, American Academy of Pediatrics, American College of Osteopathic Pediatricians, and American Osteopathic Association

Disclosure: Nothing to disclose.

Chief Editor

Bruce Buehler, MD  Professor, Department of Pediatrics and Genetics, Director RSA, University of Nebraska Medical Center

Bruce Buehler, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Pediatrics, American Association on Mental Retardation, American College of Medical Genetics, American College of Physician Executives, American Medical Association, and Nebraska Medical Association

Disclosure: Nothing to disclose.

References

  1. Yefimenko I, Frequet V, Marco-Marin C, et al. Understanding carbomyl phosphate synthetase deficiency: impact of clinical mutations on enzyme functionality. J Mol Biol. 2005;349:127-141.

  2. Keskinen P, Siitonen A, Salo M. Hereditary urea cycle diseases in Finland. Acta Paediatr. Oct 2008;97(10):1412-9. [Medline].

  3. Funghini S, Thusberg J, Spada M, Gasperini S, Parini R, Ventura L, et al. Carbamoyl phosphate synthetase 1 deficiency in Italy: clinical and genetic findings in a heterogeneous cohort. Gene. Feb 10 2012;493(2):228-34. [Medline].

  4. Wong LJ, Craigen WJ, O'Brien WE. Postpartum coma and death due to carbamoyl-phosphate synthetase I deficiency. Ann Intern Med. Feb 1 1994;120(3):216-7. [Medline].

  5. Häberle J, Shchelochkov OA, Wang J, Katsonis P, Hall L, Reiss S, et al. Molecular defects in human carbamoy phosphate synthetase I: mutational spectrum, diagnostic and protein structure considerations. Hum Mutat. Jun 2011;32(6):579-89. [Medline].

  6. Batshaw ML, Brusilow S, Waber L, Blom W, et al. Treatment of inborn errors of urea synthesis: activation of alternative pathways of waste nitrogen synthesis and excretion. N Engl J Med. Jun 10 1982;306(23):1387-92. [Medline].

  7. Berry GT, Steiner RD. Long-term management of patients with urea cycle disorders. J Pediatr. Jan 2001;138(1 Suppl):S56-60; discussion S60-1. [Medline].

  8. Eather G, Coman D, Lander C, et al. Carbamyl phosphate synthase deficiency: diagnosed during pregnancy in a 41-year-old. J Clin Neurosci. 2006;13:702-6.

  9. Eeds AM, Hall LD, Yadav M, et al. The frequent observation of evidence for nonsense-mediated decay in RNA from patients with caramyl phosphate synthetase I deficiency. Mol Genet Metab. 2006;89:80-86.

  10. Farriaux JP, Ponte C, Pollitt RJ, Lequien P, et al. Carbamyl-phosphate-synthetase deficiency with neonatal onset of symptoms. Acta Paediatr Scand. Jul 1977;66(4):529-34. [Medline].

  11. Finckh U, Kohlschutter A, Schafer H, Sperhake K, et al. Prenatal diagnosis of carbamoyl phosphate synthetase I deficiency by identification of a missense mutation in CPS1. Hum Mutat. 1998;12(3):206-11. [Medline].

  12. Freeman JM, Nicholson JF, Schimke RT, Rowland LP, et al. Congenital hyperammonemia. Association with hyperglycinemia and decreased levels of carbamyl phosphate synthetase. Arch Neurol. Nov 1970;23(5):430-7. [Medline].

  13. Gropman AL, Summar M, Leonard JV. Neurological implications of urea cycle disorders. J Inherit Metab Dis. Nov 2007;30(6):865-79. [Medline].

  14. Kojic J, Robertson PL, Quint DJ. Brain glutamine by MRS in a patient with urea cycle disorder and coma. Pediatr Neurol. 2005;32:143-146.

  15. Steiner RD, Cederbaum SD. Laboratory evaluation of urea cycle disorders. J Pediatr. Jan 2001;138(1 Pt 2):S21-S29.

  16. Summar ML. Molecular genetic research into carbamoyl-phosphate synthase I: molecular defects and linkage markers. J Inherit Metab Dis. 1998;21 Suppl 1:30-9. [Medline].

  17. Summar ML, Hall L, Christman B. Environmentally determined genetic expression: clinical correlates with molecular variants of carbamyl phosphate synthetase I. Mol Genet Metab. 2004;81Supplement 1:S12-S19.

  18. Verbiest HB, Straver JS, Colombo JP, van der Vijver JC, et al. Carbamyl phosphate synthetase-1 deficiency discovered after valproic acid-induced coma. Acta Neurol Scand. Sep 1992;86(3):275-9. [Medline].

 
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Compounds comprising the urea cycle are numbered sequentially, beginning with carbamyl phosphate (1). At this step, the first waste nitrogen is incorporated into the cycle; at this step, N-acetylglutamate exerts its regulatory control on the mediating enzyme, carbamyl phosphate synthetase (CPS). Compound 2 is citrulline, the product of condensation between carbamyl phosphate (1) and ornithine (8); the mediating enzyme is ornithine transcarbamylase. Compound 3 is aspartic acid, which is combined with citrulline to form argininosuccinic acid (ASA) (4); the reaction is mediated by ASA synthetase. Compound 5 is fumaric acid generated in the reaction that converts ASA to arginine (6), which is mediated by ASA lyase.
 
 
 
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