29 Questions
Which type of genetic disorder is caused by defects in the mitochondrial genome?
Mitochondrial myopathies
What is the primary cause of Leigh's syndrome?
Defect in complex I of the electron transport chain
Which of the following is not a key feature for suspecting an inborn error of metabolism?
Increased blood pressure
What is the primary reason for diagnosing inborn errors of metabolism?
To offer genetic counseling and antenatal diagnosis
What is the main inheritance pattern for mitochondrial diseases?
Maternal
Which of the following is a common feature of inborn errors of metabolism?
Collectively accounting for a significant proportion of neonatal and childhood morbidity and mortality
Which of the following conditions would NOT typically prompt consideration of an inborn error of metabolism?
Recurrent infections
What is the normal range for plasma ammonia levels in newborns?
90-150 mg/dL
Which of the following is NOT considered a first-line investigation for suspected inborn errors of metabolism?
Electroencephalogram
What is the normal range for arterial blood lactate levels?
0.5-1.6 mmol/L
Why is it important to initiate metabolic investigations as soon as the possibility of an inborn error of metabolism is considered?
The outcome of treatment is directly related to the rapidity of detection and treatment
Which of the following is NOT typically considered a clinical pointer towards a specific inborn error of metabolism?
Recurrent vomiting
What is the term used to describe rare genetic (inherited) disorders due to defects of single genes that code for enzymes?
Inborn errors of metabolism
Who was the first to propose the idea of 'Inborn error of metabolism'?
Archibald Edward Garrod
What is the process of breaking down molecules into smaller units and releasing energy called?
Catabolism
What is the role of enzymes in the metabolic process?
Enzymes facilitate the conversion of one chemical (metabolite) to another by serving as catalysts.
What is the term used to describe the set of metabolic pathways that build up molecules?
Anabolism
What is the main rationale for hematopoietic cell transplantation (HCT) in inborn errors of metabolism (IEMs)?
To provide correcting enzymes by donor cells within and outside the blood compartment
What is the recurrence risk for most inborn errors of metabolism (IEMs)?
25%
Which of the following is not a sample required for prenatal diagnosis of inborn errors of metabolism (IEMs)?
Fetal blood
Which of the following is a modality used for prenatal diagnosis of inborn errors of metabolism (IEMs)?
All of the above
What is the main limitation of tandem mass spectrometry (TMS) for neonatal screening of inborn errors of metabolism (IEMs)?
It is not specific enough, and there are difficulties in interpreting abnormal test results in apparently healthy infants
Which of the following inborn errors of metabolism (IEMs) can be detected by tandem mass spectrometry (TMS) in neonatal screening?
Aminoacidopathies, fatty acid oxidation defects, and organic acidemias
Which of the following is NOT a characteristic of anabolism?
It breaks down complex molecules
In the example of mechanisms in IEM, what does the letter 'A' represent?
Substrate
Which of the following groups of inborn errors of metabolism is characterized by acute or chronic intoxications?
Group 2 (intermediary metabolism)
Which of the following disorders is considered mostly untreatable?
Mitochondrial defects
What is the primary cause of inborn errors of metabolism?
Mutations in DNA
Which of the following treatments is NOT mentioned for inborn errors of metabolism?
Gene therapy
Study Notes
Inborn Errors of Metabolism (IEM)
- Inborn errors of metabolism are rare genetic disorders caused by defects of single genes that code for enzymes.
- These disorders are usually caused by defects in enzymes involved in biochemical pathways that break down essential biochemical components.
History of IEM
- Sir Archibald Edward Garrod was the first to propose the idea of “Inborn error of metabolism”.
- Garrod was the first to connect a human disorder with Mendel's laws of inheritance.
- He also proposed the idea that diseases come about through a metabolic route leading to the molecular basis of inheritance.
Metabolism
- Metabolism involves two types of processes: catabolism and anabolism.
- Catabolism breaks down molecules into smaller units and releases energy.
- Anabolism constructs molecules from smaller units and requires energy.
Mitochondrial Inheritance
- Mitochondrial genes are inherited only from the mother.
- Defects in mitochondrial genes can lead to diseases such as Leber's hereditary optic neuropathy, mitochondrial myopathies, and Leigh's syndrome.
Classification of IEM
- IEM can be classified into six categories: carbohydrate metabolism, organic acid metabolism, lipid metabolism, protein metabolism, amino acid metabolism, and mitochondrial fatty acid oxidation.
Approaching IEM
- Suspecting IEM: look for symptoms accompanying diet changes, seizures, developmental delay, recurrent vomiting, unusual odor of urine, parental consanguinity, and unexplained deaths in relatives.
- Investigations: initiate metabolic investigations as soon as possible, including CBC, blood glucose, electrolytes, and liver function tests.
- Treatment: may involve enzyme replacement therapy, transplantation, and gene therapy.
- Prevention: genetic counseling, prenatal diagnosis, and neonatal screening can help prevent IEM.
Classification of IEM into Three Pathophysiological Diagnostic Groups
- Group 1: Anabolism/catabolism disorders
- Group 2: Intermediary metabolism disorders, including urea cycle disorders and some lysosomal disorders
- Group 3: Energy production/utilization disorders, including mitochondrial defects
Test your knowledge on the molecular basis of inborn errors of metabolism with this quiz based on the teachings of Dr. Nermin Eissa at Abu Dhabi University. Explore rare genetic disorders caused by defects in single genes coding for enzymes, leading to disruptions in biochemical pathways.
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