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Virology- MHD > Inborn Errors of Metabolism > Flashcards

Inborn Errors of Metabolism Flashcards

1
Q

How do organic acidurias present clinically?

A

Decomposition within the first two weeks of life

Acidosis, elevated anion gap, elevated lactic acid, hypoglycemia

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2
Q

Name 4 acids that contribute to organic acidemia

A

Methylmalonic
Isovaleric
Proprionic
Glutaric acidemia

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3
Q

List some clinical features of organic acidemia

A 
Ketoacidosis
Elevated glycine
Hypoglycemia
Bone marrow suppression
Hyperammonemia (200-600
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4
Q

Describe how PKU leads to an amino acidemia

A

When phenylalanine hydroxylase (PAH) is nonfunctioning, phenylalanine can no longer be converted to tyrosine and is instead shunted to phenylpyruvate which is subsequently converted to acids

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5
Q

What is the main clinical problem with PKU?

A

The acids that accumulate in the blood are toxic to the brain. If untreated, infants can lose up to 50 IQ points within the first year of life

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6
Q

What is the purpose of the urea cycle?

A

Dispose of nitrogen waste and the biosynthesis of arginine

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7
Q

What is the main problem when the urea cycle doesn’t work properly?

A

The NH3 builds up in the blood

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8
Q

What is the most common cause of a urea cycle deficiency?

A

X-linked OTC (ornithine transcarbamylase)

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9
Q

Are people with a urea cycle deficiency alkalotic or acidotic?

A

Alkalotic- due to build-up of NH3 in the blood

NH3 can reach the 1000’s

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10
Q

What are the symptoms of nonketotic hyperglycinemia?

A

Progressive lethargy, hypotonia, myotonic jerks and apnea

Some babies have hiccups

(elevated glycine)

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11
Q

What are the findings on MRI of someone with nonketotic hyperglycinemia?

A

Agenesis of the corpus callosum

Majority of the infants die- if they survive they have profound mental retardation

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12
Q

How are the ammonia, lactate and glucose levels in a baby with maple syrup urine disease?

A

NH3: normal or elevated
Lactate: normal
glucose: normal

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13
Q

What does the baby have if the urine smells like sweaty feet?

A

Isovaleric acidemia

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14
Q

What does the baby have if the urine smells like rotten cabbage?

A

Tyrosinemia

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15
Q

What is the problem in medium-chain acyl-coenzyme A dehydrogenase deficiency (MCAD)?

A

Deficiency in an enzyme involved in mitochondrial fatty acid beta oxidation

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16
Q

When do symptoms occur with MCAD?

A

After prolonged fasting

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17
Q

Can MCAD be deadly?

A

2-3% of SIDS is caused by MCAD

18
Q

What are the symptoms of MCAD?

A

Hypoketotic hypoglycemia- Reye-like syndrome

19
Q

What is the treatment for MCAD deficiency

A

carnitine supplementation,

20
Q

Describe the symptoms associated with MCAD

A

Episodic illness with hypoglycemia usually between 3 months and 2 years of age- usually follows fasting of 12 hours or more with infectious illness

Acute episode starts with vomiting, lethargy, or even seizures

Can progress to coma rapidly

21
Q

Is the urine dip positive or negative for ketones with MCAD?

A

NEGATIVE- ketones come from beta oxidation of fatty acids. This process is busted in MCAD

22
Q

What is the MRI finding suggestive of glutartic acidemia?

A

Subdural hematomas

23
Q

Is the onset of glutaric acidemia immediate or delayed onset after birth?

A

Delayed onset

24
Q

What is the enzyme deficient in galactosemia?

A

Galactose-1-P-uridyl transferase (GALT)

Could also be GALK or GALE

25
Q

What toxic metabolite builds up in galactosemia?

A

Galactitol

26
Q

What positive lab findings are seen in the urine of someone with galactosemia?

A

Reducing substances (unmetabolized sugars)

27
Q

List the important clinical features of galactosemia

A

E. COLI SEPSIS
Jaundice
Hepatomegaly
CATARACTS

Untreated babies can rapidly progress to hepatic and death from sepsis or bleeding

28
Q

What is the treatment for galactosemia?

A

Lactose free diet

During infancy- use Soy formula (breast milk has lactose)

29
Q

What is the enzyme deficient in glycogen disorder type I?

A

Von Gierke’s disease;

Enzyme is glucose-6-phosphatase. Glucose-6-P cannot be cleaved to glucose and is therefore stuck in the cell

30
Q

Describe the body of a baby with von gierks?

A

Shows failure to thrive- thin limbs and large abdomen

31
Q

What is the treatment for type I glycogen storage disease?

A

Prevent hypoglycemia with continuous feeds or cornstartch

Restrict galactose and fructose in the diet

32
Q

What is the enzyme deficiency in type III glycogen storage disease?

A

Cori’s disease:

Deficiency of glycogen debranching enzymes. Complete degradation of glycogen is not possible –> abnormal glycogen/build up

33
Q

What are the clinical features of Cori’s disease/

A 
Hepatomegaly
Hypoglycemia
Short stature
Skeletal myopathy
Cardiomyopathy
34
Q

Which glycogen storage disease affects the liver?

A

I, 3, 4, 6

35
Q

Which glycogen storage diseases affect the skeletal muscle?

A

2, 5, 7

36
Q

What is the enzyme responsible for McArdle’s disease?

A

Muscle phosphorylase –> results in reduced ATP generation by glycogenolysis

37
Q

What are the clinical signs of McArdle’s?

A

Symptoms begin in the early 20’s
Exercise induced muscle cramps and exercise intolerance
BURGUNDY COLORED URINE

Labs show elevated CPK at rest, increases significantly with exercise

38
Q

What is the treatment for McArdle’s?

A

Avoid strenuous exercise

39
Q

What is the enzyme deficient in type VII glycogen storage disease?

A

Phosphofructokinase deficiency- no conversion of fructose-6-phosphate to fructose-1,6-bisphosphate

40
Q

How does type VII differ from McArdle’s?

A

Presents in childhood
Hemolysis occurs
Increases uric acid levels
Exercise intolerance is much worse after a carbohydrate meal

Virology- MHD (17 decks)

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