Inborn Errors of Metabolism Quiz
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Questions and Answers

What is a consequence of acute tyrosinemia due to the absence of the enzyme FAH?

  • Accumulation of toxic metabolic products (correct)
  • Increased insulin resistance
  • Development of cirrhosis in early childhood
  • Deficiency of vitamin K

    • Which symptom is NOT commonly associated with chronic tyrosinemia in children?

  • Enlarged liver and spleen
  • Distended abdomen with fluid
  • Poor weight gain
  • Increased blood pressure (correct)

    • What is a major phenotypic manifestation of homocystinuria?

  • Bleeding tendency
  • Maple syrup odor in urine
  • Enlarged liver
  • Ectopia lentis (correct)

    • Which condition is characterized by a maple syrup odor and leads to severe illness shortly after birth?

    <p>Maple syrup urine disease (C)</p> Signup and view all the answers

    Which diagnostic technique is used to identify phenylketonuria?

    <p>Guthrie bacterial inhibition assay (C)</p> Signup and view all the answers

    What is a common characteristic of inborn errors of metabolism (IEM)?

    <p>They are usually autosomal recessive. (C)</p> Signup and view all the answers

    Which of the following diseases is characterized by a musty or mousy odor in urine?

    <p>Phenylketonuria (PKU) (D)</p> Signup and view all the answers

    Which disorder is associated with a defect in the enzyme homogentisate 1,2-dioxygenase?

    <p>Alkaptonuria (A)</p> Signup and view all the answers

    Which of the following symptoms indicates glutaric acidemia type II?

    <p>Respiratory distress (D)</p> Signup and view all the answers

    What is the likely consequence of untreated Phenylketonuria (PKU)?

    <p>Cataracts and skin disorders (A)</p> Signup and view all the answers

    Which amino acid disorder causes urine to have a rotten fish odor?

    <p>Trimethylaminuria (D)</p> Signup and view all the answers

    In the context of IEM, what is primarily affected by a defect in enzyme activity?

    <p>Amino acid degradation and synthesis (B)</p> Signup and view all the answers

    What clinical feature is an indication of ornithine transcarbamylase deficiency?

    <p>Acute metabolic crisis (D)</p> Signup and view all the answers

    Flashcards

    Acute Tyrosinemia

    Caused by a lack of the fumarylacetoacetate hydrolase enzyme (FAH), leading to a build-up of toxic substances in the body, primarily affecting the liver and kidneys.

    Chronic Tyrosinemia

    Characterized by an enlarged liver and spleen, fluid buildup in the abdomen, poor weight gain, frequent vomiting and diarrhea, and often leading to cirrhosis.

    Homocystinuria

    A genetic metabolic disorder caused by a deficiency in cystathionine synthase, leading to the accumulation of homocysteine and methionine in the body.

    Maple Syrup Urine Disease

    A rare genetic disorder resulting in a buildup of branched-chain amino acids in the body, leading to a distinctive maple syrup odor in urine and severe neurological problems.

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    Albinism

    Caused by a deficiency in the enzyme tyrosinase, leading to a lack of melanin production, resulting in light skin, hair, and eyes.

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    Inborn Error of Metabolism (IEM)

    A group of genetic disorders where the body cannot break down food components normally due to defects in enzymes involved in metabolic pathways.

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    Amino Acid Inborn Error of Metabolism (IEM)

    A type of IEM where defects in enzyme or transport proteins block metabolic pathways for amino acids, leading to toxic accumulation of substrates.

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    Alkaptonuria (Black Urine Disease)

    A rare genetic disorder where the body cannot break down tyrosine effectively. This leads to accumulation of homogentisic acid in blood and urine, causing damage to cartilage, heart valves, and kidney stones.

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    Phenylketonuria (PKU)

    A serious IEM where the body can't break down phenylalanine properly. This causes it to build up in the blood, leading to brain damage, developmental disabilities, and other health problems.

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    Ornithine Transcarbamylase Deficiency (Urea Cycle Disorder)

    A life-threatening IEM causing a buildup of ammonia in the blood due to defects in the urea cycle. Leads to severe symptoms like vomiting, coma, and respiratory distress.

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    Tyrosinemia

    A genetic IEM causing severe liver disease in infancy due to defects in tyrosine metabolism. Leads to accumulation of toxic substances in the body.

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    Urine Odor in IEMs

    A characteristic symptom of IEMs where the urine has a specific odor due to the accumulation of metabolic by-products.

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    Characteristic Odors in IEMs

    Distinct odors associated with specific IEMs, such as 'maple syrup' in maple syrup urine disease, 'mousy' in phenylketonuria, and 'rotten fish' in trimethylaminuria.

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    Study Notes

    Inborn Errors of Metabolism (IEM) - Amino Acid Disorders

    • IEMs are usually autosomal recessive genetic disorders.
    • Diagnosis confirmed by biochemical assays of metabolites, DNA studies, and neuro-radiology.
    • These disorders affect amino acid metabolism, impacting synthesis and degradation.
    • IEMs arise from enzyme or transport protein defects, hindering metabolic pathways and leading to substrate buildup.

    Specific Amino Acid Transport Disorders

    • Cystinuria: Amino acid transport disorder.
    • Dicarboxylic aminoaciduria: Amino acid transport disorder.
    • Hartnup disease: Amino acid transport disorder.

    Specific Amino Acid Storage Disorders

    • Glutaric acidemia type II: Amino acid storage disorder.

    Characteristic Symptoms and Diagnoses

    • Urine odor: Provides clues to specific disorders—

      • Maple syrup urine disease: Maple syrup odor.
      • Glutaric acidemia: Sweaty feet odor.
      • Phenylketonuria (PKU): Mousy or musty odor.
      • Trimethylaminuria: Rotten fish odor.

    • Specific IEMs and their characteristics:

      • Phenylketonuria (PKU): Silent until untreated; leads to brain damage and developmental issues. Elevated phenylalanine levels (30-50 times normal) result in phenylalanine metabolites.
      • Ornithine transcarbamylase (OTC) deficiency: Type 2 is life-threatening in infancy. Acute metabolic crisis marked by vomiting, respiratory issues, lethargy, and possible coma.
      • Tyrosinemia: Hereditary; severe liver disease in infancy (autosomal recessive). Lack of fumarylacetoacetate hydrolase (FAH) enzyme causes a buildup of toxic metabolites; progressive liver and kidney damage results from this build up.
        • Acute tyrosinemia: Poor weight gain, enlarged liver, swelling, bleeding tendency are seen in infants, frequently lethal before nine months without intervention.
        • Chronic tyrosinemia: Enlarges liver/spleen, fluid build-up, poor weight gain, frequent vomiting/diarrhea. Eventually leads to cirrhosis; liver transplant needed.
      • Homocystinuria: Phenotypic expression includes ectopia lentis, vascular disease, malar flush, osteoporosis, accumulation of homocysteine/methionine. Defective cystathionine synthase activity is the cause.
      • Maple syrup urine disease: Severe illness in infants, lethargy progressing to coma, seizures, developmental delay, maple syrup odor. Branched-chain aminoacidemia and aminoaciduria.

    • Alkaptonuria: "Black urine disease"; defect in homogentisate 1,2-dioxygenase enzyme. Homogentisic acid (alkapton) accumulates, causing cartilage damage (ochronosis/osteoarthritis), heart valve issues, and kidney stones.

    Diagnostic Techniques

    • Ferric chloride test: Used in diagnosis (for general).
    • Ninhydrin paper chromatography: Used for diagnosis.
    • Guthrie bacterial inhibition assay: Used in the diagnosis of PKU.
    • Quantitative measurements of amino acids in plasma and urine: Used.
    • GC for urine organic acid analysis: Used for diagnosis.
    • Paper/TLC, plasma and urine: Can be used for diagnosis
    • Plasma levels: 6.6 mg/ml
    • Urine levels: 3.12 mmol/mmol of creatinine

    Albinism

    • Tyrosinase deficiency causes hair and skin pigment loss;
    • Individuals with PKU may have light skin/hair at birth because of low tyrosine levels.

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    Description

    Test your knowledge on Inborn Errors of Metabolism (IEM) and the various amino acid disorders. This quiz covers specific transport and storage disorders, characteristics, and symptoms associated with these metabolic disorders. Challenge yourself and deepen your understanding of these genetic conditions.

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