Ornithine transcarbamylase deficiency

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Ornithine transcarbamylase deficiency

Biochemistry

Biochemistry and metabolism

Amino acid metabolism
Nitrogen and urea cycle
Citric acid cycle
Electron transport chain and oxidative phosphorylation
Gluconeogenesis
Glycogen metabolism
Glycolysis
Pentose phosphate pathway
Physiological changes during exercise
Cholesterol metabolism
Fatty acid oxidation
Fatty acid synthesis
Ketone body metabolism

Metabolic disorders

Alkaptonuria
Cystinuria (NORD)
Hartnup disease
Homocystinuria
Maple syrup urine disease
Ornithine transcarbamylase deficiency
Phenylketonuria (NORD)
Essential fructosuria
Galactosemia
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hereditary fructose intolerance
Lactose intolerance
Pyruvate dehydrogenase deficiency
Abetalipoproteinemia
Familial hypercholesterolemia
Hyperlipidemia
Hypertriglyceridemia
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Fabry disease (NORD)
Gaucher disease (NORD)
Krabbe disease
Leukodystrophy
Metachromatic leukodystrophy (NORD)
Niemann-Pick disease type C
Niemann-Pick disease types A and B (NORD)
Tay-Sachs disease (NORD)
Cystinosis
Disorders of amino acid metabolism: Pathology review
Disorders of carbohydrate metabolism: Pathology review
Disorders of fatty acid metabolism: Pathology review
Dyslipidemias: Pathology review
Glycogen storage disorders: Pathology review
Lysosomal storage disorders: Pathology review

Assessments

Flashcards

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USMLE® Step 1 questions

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High Yield Notes

7 pages

Flashcards

Ornithine transcarbamylase deficiency

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Questions

USMLE® Step 1 style questions USMLE

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A 4-day-old female neonate is under evaluation in the neonatal ICU following a seizure-like episode. Since starting breastfeeding, she has been irritable and feeding poorly, and she has had several episodes of vomiting. She was born at 29 weeks gestation to a 29-year-old woman following a caesarean delivery for prolonged labor. The patient has been exclusively breastfed since birth. Temperature is 36.4°C (97.5°F), pulse is 145/min, and respiratory rate is 67/min. On physical examination, the patient appears somnolent and lethargic. Skin turgor is delayed and eyes appear sunken. Abdominal examination is unremarkable. Neurological examination reveals diffuse hypotonia and somnolence without response to painful stimulation. Sepsis workup is negative. Laboratory evaluation reveals orotic aciduria and hyperammonemia. Serum arginine levels are within normal limits. Deficiency of which of the following enzymes is responsible for this patient’s symptoms? 

External References

First Aid

2024

2023

2022

2021

Ammonia

Ornithine transcarbamylase deficiency p. 81

BUN (blood urea nitrogen)

ornithine transcarbamylase deficiency p. 81

Ornithine transcarbamylase deficiency p. 59, 81

Urea cycle p. 80

ornithine transcarbamylase deficiency and p. 81

Summary

Ornithine transcarbamylase deficiency (OTC deficiency) is an x-linked genetic disorder characterized by a deficiency of the enzyme ornithine transcarbamylase. OTC enzyme is responsible for breaking down excess ammonia, a byproduct of protein metabolism, and is normally eliminated by the liver. When OTC deficiency is present, ammonia builds up in the body, which can lead to serious health problems.

Symptoms of OTC deficiency may include vomiting, diarrhea, lethargy, and poor feeding in infants, and later in life, intellectual disability and behavioral problems may develop. OTC deficiency is typically diagnosed in newborns through screening tests, and treatment may involve a low-protein diet, medications to reduce ammonia levels, and liver transplantation.