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Chem Path > Chem Path: Metabolic disorders and screening 2 > Flashcards

Chem Path: Metabolic disorders and screening 2 Flashcards

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1
Q

What are normal levels of ammonia?

A

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2
Q

What is the urea cycle?

A

Converts ammonia to urea

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3
Q

What can go wrong in the urea cycle?

A

7 enzymes involved - Can have deficiency it any of them

Lysiniuric protein intolerance
HHH
Citrullinaemia type 2

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4
Q

What happens when there is something wrong with the urea cycle?

A

Hyperammonaemia

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5
Q

How are the urea cycle disorders inherited?

A

Recessive except for OTC deficiency which is x linked

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6
Q

What happens in hyperammonaemia?

A

Glutamate is attached to it to make glutamine in an attempt to get rid of urea
So plasma glutamine rises

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7
Q

What else can you measure to diagnose hyperammonaemia and urea cycle disorders

A

Urine orotic acid

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8
Q

How is hyperammonaemia treated

A

Sodium benzoate or sodium phenylacetate or dialysis

Low protein diet

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9
Q

How do hyperammonaemia and urea cycle disorders present

A 
Respiratory alkalosis 
Vomiting without diarrhoea
Cerebral oedema 
Seizures 
Comatose
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10
Q

What are associated with urea cycle disorders

A

ADHD/ Long standing mental illness
Methandrostenolone use
Creatinine supplement

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11
Q

What happens in organic acidurias

A

Defect in metabolism of leucine or isoleucine or valine

Isovaleryl CoA (a breakdown product of the amino acids) has to be broken down by isovaleryl CoA dehydrogenase. If this enzyme is deficient, you will have to excrete the compound as 3Oh isovaleric acid

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12
Q

How does isovaleric acid smell

A

Cheesy/ Sweaty smell

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13
Q

How do organic acidurias present?

A

Hyperammonaemia with METABOLIC ACIDOSIS and high anion gap

In neonates:

Unusual odour
Lethargy, feeding problems
Truncal hypotonia and limb hypertonia
Myoclonic jerks

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14
Q

How does the chronic intermittent form of organic acidurias present in kids

A

Recurrent ketoacidotic comas
Cerebral abnormalities
Reye syndrome

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15
Q

What is Reye syndrome

A

Rapidly progressing encephalopathy

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16
Q

How does Reye syndrome present

A 
Vomiting
Lethargy 
Confusion
Seizures 
Decerebration 
Respiratory arrest
17
Q

What can Reye syndrome be triggered by

A

Salicylates (aspirin), anti emetics, valporate

18
Q

How will you screen for Reye syndrome / Organic acidurea

A

Plasma ammonia
Plasma/Urine amino acids
Urine organic acids
Plasma glucose and lactate

All of the 4 should be done during the acute episode

Blood spot carnitine profile can be done anytime

19
Q

What happens in mitochondrial fatty acid beta oxidation defect

A

You cannot break down fatty acids so there is no ketone production

20
Q

Hoe does mitochondrial fatty acid beta oxidation defect present

A

Hypoketotic hypoglycaemia
Hepatomegaly
Cardiomyopathy

21
Q

How do you test for mitochondrial fatty acid beta oxidation defect

A

Blood ketones
Urine organic acids
Blood spot acylcarnitine profile

22
Q

What are the 2 carbohydrate break down disorders

A

Galactosaemia

Glycogen storage disease type 1 (Von Gierke disease)

23
Q

What is the most common deficiency in galactosaemia

A

Gal-1-PUT deficiency

24
Q

How does Gal-1-PUT deficiency present in neonates

A 
Hepatomegaly
Hypoglycaemia 
D&V
Conjugated hyperbilirubinaemia 
Sepsis
25
Q

Why cant here be sepsis in mitochondrial fatty acid beta oxidation defect

A

Gal-1-PUT inhibits immune responses so babies can develop E Coli sepsis

26
Q

If not picked up at infancy, what can mitochondrial fatty acid beta oxidation defect cause in children

A

Bilateral cataracts as Gal-1-PUT can become a subtrate for aldolase

27
Q

How to investigate for mitochondrial fatty acid beta oxidation defect

A

Urine reducing substances

RBC Gal-1-PUT

28
Q

How tot treat mitochondrial fatty acid beta oxidation defect

A

Avoid milk (galactose)

29
Q

What happens in von Gierke disease

A

Lack of phosphatase enzyme to break down G6p and G1P. Leads to a buildup of glycogen in muscles, leading to hypoglycaemia

30
Q

How does von Gierke disease present

A 
Hepatomegaly
Nephromegaly
Hypoglycaemia 
Lactic acidosis 
Neutropaenia
31
Q

What happens in mitochondrial disorders

A

Heteroplasmy of mtDNA - Develop symptoms after reaching a certain load of mtDNA

Can present at any time, any age

Defective ATP production

32
Q

What are some examples of mitochondrial disorders in terms of age of presentation

A

Birth - Barth (Cardiomyopathy, neutropaenia, myopathy)
5-15 - MELAS (Mitochondrial encephalopathy, lactic acidosis and stroke like episodes)
12-30 - Kearns-Sayre (Chronic progressive external opthalmoplegia, retinopathy, deafness, ataxia)

33
Q

How would you investigate for mitochondrial disorders

A

High lactate - especially after fasting or before and after meals - This would usually be LOW in normal people

CSF lactate / pyruvate

CSF protein - Raised in kearns-Sayre syndrome

High CK + High lactate

Ragged red fibres in muscle biopsy

Chem Path (22 decks)

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