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32 Cards in this Set

  • Front
  • Back

What is an inborn error of metabolism?

A genetic condition which impairs the body's ability to metabolize biological substances

What are IMDs?

Inborn metabolic diseases

What define IMDs?

Diseases due to the absence, inactivity, or reduced activity of proteins which regulate metabolic pathways

What are some examples of metabolic pathways?

The Krebs cycle, glycolysis, amino acid catabolism, glycoprotein synthesis, fatty acid oxidation, urea cycle

What is Garrod's hypothesis?

The idea that having a toxic excess of substrate will cause improper conversion to the intended product, instead producing a different toxic metabolite

What are the two effects resulting from substrate excess, according to Garrod's theory?

An increase of toxic metabolite and a deficiency of product (structural, energy)

How are IMDs classified?

By the type of molecule and cell organelle effected, or by the affected metabolic pathway

What type of inheritance generally causes IMDs?

Autosomal recessive genes

What inheritance types can cause IMDs?

Autosomal recessive or dominant genes, X-linked disorders, maternal mitochondrial DNA

How common are IMDS?

Individually rare, collectively common

When do most IMDs present?

Neonatal period

How severe are neonatal IMDs?

Generally acute and life-threatening

When is it least common for IMDs to present?


What makes neonatal IMDs hard to detect?

Non-specific presentation-- can be mistaken for infection or sepsis

What are the 4 broad groups of clinical presentation?

Secondary accumulation of toxins, enegy deprivation, liver disfunction with hypoglycemia, dysmorphism

What is common in the clinical presentation of IMDs?

Overlap of symptoms (4 broad groups)

Why is there often a delay in disease onset for infants with IMDs?

Because toxin accumulation takes place over 2-3 days before becoming dangerous

What are the symptoms of IMD intoxication?

Vomiting, lethargy, coma, liver failure, acidsosi, hyperammonemia, hypoglycemia

An infant presents with vomiting, rapid breathing, lethargy, dehydration, fever, and weight loss a day or two after birth. What is the most likely cause?

Intoxication secondary to an IMD

How does an IMD with secondary energy deprivation present?

Immediate issues with hypoglycemia, sudden death in neonates

What tissues are affected in an IMD with secondary energy deprivation?

Metabolically active tissues (liver, muscle, brain)

What are the symptoms of an IMD with secondary energy deprivation in older children?

Floppiness, heart failure, cardiomyopathy, high lactic acid

How is an IMD with secondary energy deprivation treated?

Energy supplements (e.g. glucose infusion), frequent eating

A young child presents with floppiness, hypoglycaemia, and seizures after not eating for 18 hours. What is the most likely cause?

IMD with secondary energy deprivation

How does an IMD with secondary liver failure and hypoglycaemia present?

Seizures, acidosis and ketosis, hepatomegaly

A 6 week old infant presents with vomiting, hepatomegaly, jaundice, and cataracts. What is the most likely cause?

Liver failure secondary to an IMD

How does an IMD with secondary dysmorphism present?

Slow development, abnormal face or body features, hepatomegaly

A young child presents with slow development, frequent infections, hepatomegaly, and a deformed face. What is the most likely cause?

IMD with secondary dysmorphism

Where are most tests for IMDs conducted?

The Inherited Metabolic Biochemistry labs at pediatric hospitals, and later genetic laboratories

What results of a first line investigation might suggest an IMD?

Hypoglycaemia, acidosis, hyperammonia, elevated LFTS, high lactate

What types of screening exists for neonates?

PKU, MCAD, congenital adrenal hyperplasia, galactosaemia, CF

Why must a great amount of suspicion be used when diagnosing IMDs?

They are rare enough that there are more likely causes of symptoms in neonates and young children