Ornithine transcarbamylase deficiency




Ornithine transcarbamylase deficiency


Population genetics

Mendelian genetics and punnett squares

Hardy-Weinberg equilibrium

Inheritance patterns

Independent assortment of genes and linkage

Evolution and natural selection

Genetic disorders

Down syndrome (Trisomy 21)

Edwards syndrome (Trisomy 18)

Patau syndrome (Trisomy 13)

Fragile X syndrome

Huntington disease

Myotonic dystrophy

Friedreich ataxia

Turner syndrome

Klinefelter syndrome

Prader-Willi syndrome

Angelman syndrome

Beckwith-Wiedemann syndrome

Cri du chat syndrome

Williams syndrome

Alagille syndrome (NORD)


Polycystic kidney disease

Familial adenomatous polyposis

Familial hypercholesterolemia

Hereditary spherocytosis

Huntington disease

Li-Fraumeni syndrome

Marfan syndrome

Multiple endocrine neoplasia

Myotonic dystrophy


Treacher Collins syndrome

Tuberous sclerosis

von Hippel-Lindau disease


Polycystic kidney disease

Cystic fibrosis

Friedreich ataxia

Gaucher disease (NORD)

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)

Krabbe disease


Niemann-Pick disease types A and B (NORD)

Niemann-Pick disease type C

Primary ciliary dyskinesia

Phenylketonuria (NORD)

Sickle cell disease (NORD)

Tay-Sachs disease (NORD)



Wilson disease

Fragile X syndrome

Alport syndrome

X-linked agammaglobulinemia

Fabry disease (NORD)

Glucose-6-phosphate dehydrogenase (G6PD) deficiency


Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)

Lesch-Nyhan syndrome

Muscular dystrophy

Ornithine transcarbamylase deficiency

Wiskott-Aldrich syndrome

Mitochondrial myopathy

Autosomal trisomies: Pathology review

Muscular dystrophies and mitochondrial myopathies: Pathology review

Miscellaneous genetic disorders: Pathology review


Ornithine transcarbamylase deficiency


0 / 9 complete

USMLE® Step 1 questions

0 / 2 complete

High Yield Notes

7 pages


Ornithine transcarbamylase deficiency

of complete


USMLE® Step 1 style questions USMLE

of complete

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









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

External Links


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.


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