Chempath - metabolic disorders and screening Flashcards
true positive= 90
false positive = 5
true negative = 80
false negative = 10
What is the specificity?
Specificity = the probability that someone without the disease will correctly test -ve
80/85
true positive= 90
false positive = 5
true negative = 80
false negative = 10
What is the sensitivity?
Sensitivity = the probability that someone with the disease will correctly test positive
90/100
true positive= 90
false positive = 5
true negative = 80
false negative = 10
What is the positive predictive value
PPV = probability that someone with the disease will test +ve
90/95
true positive= 90
false positive = 5
true negative = 80
false negative = 10
What is the negative predictive value
NPV = probability that someone without the disease will test -ve
80/90
Phenylketonuria - what is it? what are its manifestations? how is it screened for?
Phenylalanine hydroxylase deficiency
Low IQ
measure phenylalanine levels
Congenital hypothyroidism - what is the outcome? how is it screened for?
Dysgenesis/agenesis of thyroid gland
Measure TSH levels
What level is measured in blood to screen for CF?
Immune reactive trypsin
If immune reactive trypsin level is high, what is done next?
DNA mutation detection (4)
If 2 mutations –> CF
If 1 mutation –> repeat with 28
If 0 mutations –> repeat IRT level at 3 weeks of age
Level measured in MCADD screening? how?
Acylcarnitine levels by tandem mass spec
metabolic acidosis + high anion gap + high ammonia levels + cheesy sweaty smelling urine
Isovolaeric acidaemia
Neonates with organic aciduria:
Findings on neuro exam?
Findings on ABG?
Findings on FBC?
Truncal hypotonia + limb hypertonia + myoclonic jerks
Metabolic acidosis + anion gap + high ammonia levels
Pancytopenia
Chronic intermittent form of organic acuduria?
Reye syndrome, triggered by aspirin –> Vomiting, lethargy, seizures, confusion, respiratory arrest
Eye effects in galactosaemia
Bilateral cataracts
2 major presentations of galactosaemia
1) High CONJUG BR
2) SEPSIS
Name the mitochondrial disorder that usually presents at 5-15years of age?
MELAS
= mitochondrial encephalopathy, lactic acidosis, stroke-like episodes
Hypoketotic hypoglycaemia + hepatomegaly + cardiomyopathy = ?
Mitochondrial fatty acid beta oxidation disorder
which lab investigation remains abnormal in remission of Reye syndrome?
Blood post carnitine profile
Useful lab investigations in a child who’s taken aspirin and is now lethargic + vomiting + confused + seizing
- Plasma glucose + lactate
- Plasma ammonia
- Plasma amino acids
- Urine organic acids
Which organs are particularly affected in mitochondrial disorders?
Brain, heart, kidney, retina
the latest presentation of mitochondrial disorder?
Kearns-Sayre syndrome
= ophthalmoplegia, retinopathy, deafness, ataxia
CDG type 1a = what type of disorder is this?
defect of post-translational glycosylation
wtf is a peroxisomal disorder
Defect in metabolism of v long chain fatty acids + phospholipid synthesis
a neonate has severe muscular hypotonia and dysmorphic features (+/-seizures and hepatic dysfunction). What type of metabolic disorder are you worried about?
Peroxisomal disorder
What is seen on x-ray of a child with peroxisomal disorder
calcified stippling of the patella
why does a child with peroxisomal disorder have a huge head?
Large fontanelle, which only closes at 1 year old
Which metabolic disorder leads to organomegaly and why?
Lysosomal storage disease –> substrate accumulation in organelles –> organomegally (CT, solid organs, bone, CNS, cartilage)
This leads to dysmorphia
2 Useful investigations for suspected lysosomal storage disorder (organomegaly of erryting)
- Urine mucopolysaccharides
2. Leukocyte enzyme activity
1 useful investigation for a child with suspected perixosomal disorder (severe hypotonia + huge head)
Very long chain fatty acid profile
Which lab result is super raised after fasting in mitochondrial disorders?
Lactate
How to differentiate between Reye syndrome vs mitochondrial fatty acid b-oxidation disorder?
Blood spot carnitine profile = abnormal in Reye’s
Both present with hypoketotic hypoglycaemia
MSUD - inheritance?
Autosomal recessive
MSUD is caused by…?
deficiency of branched chain keto-acid dehydrogenase complex
Brittle hair
Developmental delay
Convulsions
Homocystinuria
Cause of homocystinuria
cystathionine synthetase deficiency
PKU - appearance and smell of child?
Fair child
Musty smell
Name an eponymous syndrome which is a glycogen storage disease
Von Gierke’s
Fabry’s disease - what kind of disorder is it? how does it present (3 Fx)?
Lysosomal storage disease
LDs + dysmorphia + cherry red spot
Cherry red spot
Lysosomal storage disease eg Fabry’s
V v sweaty feet
Maple syrup urine disease
