Book contents
- Frontmatter
- Contents
- Contributing Authors
- Preface to the Third Edition
- Preface to the First Edition
- SECTION I PATHOPHYSIOLOGY OF PEDIATRIC LIVER DISEASE
- SECTION II CHOLESTATIC LIVER DISEASES
- SECTION III HEPATITIS AND IMMUNE DISORDERS
- SECTION IV METABOLIC LIVER DISEASE
- 22 Laboratory Diagnosis of Inborn Errors of Metabolism
- 23 α1-Antitrypsin Deficiency
- 24 Cystic Fibrosis Liver Disease
- 25 Inborn Errors of Carbohydrate Metabolism
- 26 Copper Metabolism and Copper Storage Disorders
- 27 Iron Storage Disorders
- 28 Heme Biosynthesis and the Porphyrias
- 29 Tyrosinemia
- 30 The Liver in Lysosomal Storage Diseases
- 31 Disorders of Bile Acid Synthesis and Metabolism: A Metabolic Basis for Liver Disease
- 32 Inborn Errors of Mitochondrial Fatty Acid Oxidation
- 33 Mitochondrial Hepatopathies
- 34 Nonalcoholic Fatty Liver Disease
- 35 Peroxisomal Diseases
- 36 Urea Cycle Disorders
- SECTION V OTHER CONDITIONS AND ISSUES IN PEDIATRIC HEPATOLOGY
- Index
- Plate section
- References
36 - Urea Cycle Disorders
from SECTION IV - METABOLIC LIVER DISEASE
Published online by Cambridge University Press: 18 December 2009
Book contents
- Frontmatter
- Contents
- Contributing Authors
- Preface to the Third Edition
- Preface to the First Edition
- SECTION I PATHOPHYSIOLOGY OF PEDIATRIC LIVER DISEASE
- SECTION II CHOLESTATIC LIVER DISEASES
- SECTION III HEPATITIS AND IMMUNE DISORDERS
- SECTION IV METABOLIC LIVER DISEASE
- 22 Laboratory Diagnosis of Inborn Errors of Metabolism
- 23 α1-Antitrypsin Deficiency
- 24 Cystic Fibrosis Liver Disease
- 25 Inborn Errors of Carbohydrate Metabolism
- 26 Copper Metabolism and Copper Storage Disorders
- 27 Iron Storage Disorders
- 28 Heme Biosynthesis and the Porphyrias
- 29 Tyrosinemia
- 30 The Liver in Lysosomal Storage Diseases
- 31 Disorders of Bile Acid Synthesis and Metabolism: A Metabolic Basis for Liver Disease
- 32 Inborn Errors of Mitochondrial Fatty Acid Oxidation
- 33 Mitochondrial Hepatopathies
- 34 Nonalcoholic Fatty Liver Disease
- 35 Peroxisomal Diseases
- 36 Urea Cycle Disorders
- SECTION V OTHER CONDITIONS AND ISSUES IN PEDIATRIC HEPATOLOGY
- Index
- Plate section
- References
Summary
The urea cycle was first described in 1932 by Krebs and Henseleit [1] (Figure 36.1). The urea cycle disorders (UCD) result from defects in the metabolism of the extra nitrogen produced by the breakdown of protein and other nitrogen-containing molecules. The incidence of these disorders in the United States is estimated to be at least 1 in 25,000 births, but partial defects may make this number much higher. In a comprehensive Japanese study covering several years the incidence was 1 in 46,000. Severe deficiency or total absence of activity of any of the first four enzymes (CPSI, OTC, ASS, and 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. In milder (or partial) urea cycle enzyme deficiencies, ammonia accumulation may be triggered by illness or stress at almost any time of life, resulting in multiple mild elevations of plasma ammonia concentration. The hyperammonemia is less severe and the symptoms more subtle. The mainstays of treatment are (1) reducing plasma ammonia concentration, (2) pharmacologic management to allow alternative pathway excretion of excess nitrogen, (3) reducing the amount of nitrogen in the diet, (4) reducing catabolism through the introduction of calories supplied by carbohydrates and fat, and (5) taking measures to reduce the risk of neurologic damage. Defects in the fifth enzyme in the pathway, arginase, result in a more subtle disease involving neurologic symptoms.
- Type
- Chapter
- Information
- Liver Disease in Children , pp. 858 - 868Publisher: Cambridge University PressPrint publication year: 2007
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