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which is the inborn error of metabolism for amino acid metabolism?
phenylketonuria
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what are the disorders related to carbohydrate metabolism?
- galactosaemia
- glycogen storage disorders
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what features in the neonate should raise suspicion of a metabolic error?
- parental consanguinity
- previous sudden infant death
- previous multiple miscarriages
- encephalopathic episodes
- severe disease in whom a diagnosis has not been forthcoming
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what is the inheritance of PKU?
autosomal recessive
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what is the defect in PKU?
- lack or absence of enzyme
- phenylalanine hydroxylase
- which converts phenylalanine to tyrosine
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what builds up in PKU and what is excreted in the urine?
- phenylalanine builds up in blood
- and get toxic byproducts - phenylacetic acid - excreted in urine
- therefore phenylketonuria
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why is newborn screening of PKU carried out?
as it is relatively common and treatable
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when is newborn screening of PKU carried out and why?
at several days of age because it is necessary for the infant to have been fed milk which contains phenylalanine
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what do infants with PKU look like at birth?
clinically normal
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when do symptoms and signs of PKU appear? what are they
- later in infancy and childhood - developmental delay 6-12 months
- neurological: mental retardation, hypertonicity, seizures, behaviour disorders, tremors
- growth retardation
- hypopigmentation: fair skin, light hair
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why do you get hypopigmentation in PKU?
due to the block in tyrosine production which is needed for melanin production
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what is Rx for PKU?
- reduce the phenylalanine content of the diet
- start early and continue until at least 6yo
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if planning a pregnancy, what is Rx for females with PKU? why?
- strict dietary restriction
- as maternal hyperphenylalaninaemia is associated with spontaneous abortion, microcephaly and CHD
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what is the classic triad of galactosaemia?
- liver dysfunction - elevated liver enzymes, jaundice
- coagulopathy
- cataracts
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when does galactosaemia present?
- when fed lactose containing foods eg breast milk or formula milk
- have poor feeding, vomiting, jaundice, hepatomegaly, hepatic failure
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what is galactosaemia associated with?
E Coli sepsis
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what is galactosaemia diagnosed by?
- presence of reducing substances in the urine
- decreased galactose-1-phosphate uridyltransferase in red cells
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what should trigger a high suspicion of galactosaemia?
severe neonatal JAUNDICE
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what is Rx of galactosaemia?
lactose and galactose free diet
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what is an absolute contraindication in galactosaemia?
breast feeding
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what is the main problem in glycogen storage disease?
enzyme defect which prevents mobilisation of glucose from glycogen resulting in abnormal storage of glycogen in liver and muscle
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the pattern of organ involvement depends on the enzyme defect, which organs can be involved?
- skeletal muscle
- liver
- heart
- brain
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what is type I glycogen storage disorder also known as? and what is the enzyme deficiency?
- von Gierke disease
- glucose-6-phosphatase
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which organ does type 1 GSD affect mostly?
liver
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what are the 3 main clinical features of type 1 GSD?
- hepatomegaly
- growth failure
- hypoglycaemia
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what is Rx of GSD?
- maintain blood glucose by frequent feeds throughout day and night
- so may need gastrostomy or NG tube feeding in infants
- older children - slow release oligosaccharides eg corn starch
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what may a girl with type 1 GSD look like?
- truncal obesity
- distended abdomen due to enlarged liver
- short stature
- hypotrophic muscles
- doll facies
- NG tube feed to maintain blood glucose levels at night
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what are the long term complications of type 1 GSD?
- hyperlipidaemia
- hyperuricaemia
- hepatic adenomas
- cardiovascular disease
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which systems of the body do MPS affect?
- CNS
- eyes
- heart
- skeletal system
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how do MPS present?
- developmental delay following a period of normal growth and development - present in first year
- coarse facies - but usually normal at birth
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what is MPS1 known as?
Hurler syndrome
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what are clinical features of Hurler syndrome?
- coarse facial features
- corneal opacities
- hepatosplenomegaly
- kyphosis
- mental retardation
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how is diagnosis of MPS made?
- identify enzyme defect
- identify excretion in urine of major storage substances - GAG glycosaminoglycans
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what is Rx of MPS?
bone marrow transplant if done early
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what is the inheritance of most MPS?
auto recessive
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