Inborn errors of metabolism.txt
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which is the inborn error of metabolism for amino acid metabolism?
what are the disorders related to carbohydrate metabolism?
- glycogen storage disorders
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
what is the inheritance of PKU?
what is the defect in PKU?
- lack or absence of enzyme
- phenylalanine hydroxylase
- which converts phenylalanine to tyrosine
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
why is newborn screening of PKU carried out?
as it is relatively common and treatable
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
what do infants with PKU look like at birth?
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
why do you get hypopigmentation in PKU?
due to the block in tyrosine production which is needed for melanin production
what is Rx for PKU?
- reduce the phenylalanine content of the diet
- start early and continue until at least 6yo
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
what is the classic triad of galactosaemia?
- liver dysfunction - elevated liver enzymes, jaundice
when does galactosaemia present?
- when fed lactose containing foods eg breast milk or formula milk
- have poor feeding, vomiting, jaundice, hepatomegaly, hepatic failure
what is galactosaemia associated with?
E Coli sepsis
what is galactosaemia diagnosed by?
- presence of reducing substances in the urine
- decreased galactose-1-phosphate uridyltransferase in red cells
what should trigger a high suspicion of galactosaemia?
severe neonatal JAUNDICE
what is Rx of galactosaemia?
lactose and galactose free diet
what is an absolute contraindication in galactosaemia?
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
the pattern of organ involvement depends on the enzyme defect, which organs can be involved?
- skeletal muscle
what is type I glycogen storage disorder also known as? and what is the enzyme deficiency?
- von Gierke disease
which organ does type 1 GSD affect mostly?
what are the 3 main clinical features of type 1 GSD?
- growth failure
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
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
what are the long term complications of type 1 GSD?
- hepatic adenomas
- cardiovascular disease
which systems of the body do MPS affect?
- skeletal system
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
what is MPS1 known as?
what are clinical features of Hurler syndrome?
- coarse facial features
- corneal opacities
- mental retardation
how is diagnosis of MPS made?
- identify enzyme defect
- identify excretion in urine of major storage substances - GAG glycosaminoglycans
what is Rx of MPS?
bone marrow transplant if done early
what is the inheritance of most MPS?
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