Q: Which of the following equations best represents the conversion that is defective in galactosemia?

$$\text{Galactose} \xrightarrow{\text{GALT}} \text{Glucose}$$

Q: Which equation best represents the defective metabolic step in phenylketonuria (PKU)?

$$\text{Phenylalanine} \xrightarrow{\text{PAH}} \text{Tyrosine}$$

Question 1

Which of the following best describes the underlying cause of most inborn errors of metabolism (IEM)?

Accepted Answer

Genetic abnormalities affecting the function or presence of metabolic enzymes

Question 2

A patient with von Gierke disease (Type I glycogen storage disorder) is unable to release glucose from glycogen. Which enzyme is deficient in this condition?

Accepted Answer

Glucose-6-phosphatase

Question 3

Which clinical feature is most likely to be observed in an infant with galactosemia who continues to consume lactose-containing foods?

Accepted Answer

Jaundice, vomiting, lethargy, and convulsions

Question 4

Phenylketonuria (PKU) is caused by a deficiency in which enzyme, and what is the consequence of this deficiency?

Accepted Answer

Phenylalanine hydroxylase; accumulation of phenylalanine leading to neurotoxicity

Question 5

A newborn presents with sweet-smelling urine, poor feeding, and lethargy. Which metabolic disorder is most likely, and which amino acids are involved?

Accepted Answer

Maple Syrup Urine Disease; leucine, isoleucine, valine

Question 6

Which of the following equations best represents the conversion that is defective in galactosemia?

Accepted Answer

$$	ext{Galactose} \xrightarrow{	ext{GALT}} 	ext{Glucose}$$

Question 7

A child with hereditary fructose intolerance should avoid which enzyme substrate to prevent toxic build-up?

Accepted Answer

Fructose

Question 8

Which organ is most likely to be enlarged in a patient with a glycogen storage disorder due to fat and glycogen accumulation?

Accepted Answer

Liver

Question 9

Which of the following best explains why untreated protein metabolic disorders often result in mental retardation?

Accepted Answer

Accumulation of toxic amino acid metabolites disrupts brain development

Question 10

Gaucher disease is caused by a deficiency of which enzyme, and what is the main consequence?

Accepted Answer

Glucocerebrosidase; accumulation of fatty material in organs

Question 11

Which of the following is the correct inheritance pattern for phenylketonuria (PKU)?

Accepted Answer

Autosomal recessive

Question 12

A patient with Niemann-Pick disease has a deficiency in acid sphingomyelinase. What is the result of this deficiency?

Accepted Answer

Accumulation of sphingomyelin in lysosomes leading to cell death

Question 13

Which diagnostic approach is most likely to identify a genetic mutation responsible for an inborn error of metabolism?

Accepted Answer

Genetic testing of DNA sequence

Question 14

A newborn screening test detects elevated phenylalanine levels. What dietary intervention should be recommended?

Accepted Answer

Restrict dietary phenylalanine

Question 15

Which equation best represents the defective metabolic step in phenylketonuria (PKU)?

Accepted Answer

$$	ext{Phenylalanine} \xrightarrow{	ext{PAH}} 	ext{Tyrosine}$$

Question 16

Which of the following symptoms is most characteristic of Maple Syrup Urine Disease (MSUD) in infants?

Accepted Answer

Sweet-smelling, low viscosity urine

Question 17

A patient with a lipid storage disease presents with neurological symptoms and hepatosplenomegaly. Which two diseases should be considered?

Accepted Answer

Gaucher Disease and Niemann-Pick Disease

Question 18

Which prenatal diagnostic test is most appropriate for detecting chromosomal abnormalities associated with metabolic disorders?

Accepted Answer

Amniocentesis

Question 19

A patient with hereditary fructose intolerance is unable to metabolize fructose due to a deficiency in which enzyme?

Accepted Answer

Aldolase B

Question 20

Which of the following best explains why metabolic disorders can be difficult to diagnose?

Accepted Answer

Symptoms often mimic more common diseases and there are thousands of possible disorders

Mendelian Disorders: Inborn Errors of Metabolism (IEM)

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