Inborn errors of metabolism.txt

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Inborn errors of metabolism.txt
2011-06-22 07:39:55

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  1. which is the inborn error of metabolism for amino acid metabolism?
  2. what are the disorders related to carbohydrate metabolism?
    • galactosaemia
    • glycogen storage disorders
  3. 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
  4. what is the inheritance of PKU?
    autosomal recessive
  5. what is the defect in PKU?
    • lack or absence of enzyme
    • phenylalanine hydroxylase
    • which converts phenylalanine to tyrosine
  6. 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
  7. why is newborn screening of PKU carried out?
    as it is relatively common and treatable
  8. 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
  9. what do infants with PKU look like at birth?
    clinically normal
  10. 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
  11. why do you get hypopigmentation in PKU?
    due to the block in tyrosine production which is needed for melanin production
  12. what is Rx for PKU?
    • reduce the phenylalanine content of the diet
    • start early and continue until at least 6yo
  13. 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
  14. what is the classic triad of galactosaemia?
    • liver dysfunction - elevated liver enzymes, jaundice
    • coagulopathy
    • cataracts
  15. when does galactosaemia present?
    • when fed lactose containing foods eg breast milk or formula milk
    • have poor feeding, vomiting, jaundice, hepatomegaly, hepatic failure
  16. what is galactosaemia associated with?
    E Coli sepsis
  17. what is galactosaemia diagnosed by?
    • presence of reducing substances in the urine
    • decreased galactose-1-phosphate uridyltransferase in red cells
  18. what should trigger a high suspicion of galactosaemia?
    severe neonatal JAUNDICE
  19. what is Rx of galactosaemia?
    lactose and galactose free diet
  20. what is an absolute contraindication in galactosaemia?
    breast feeding
  21. 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
  22. the pattern of organ involvement depends on the enzyme defect, which organs can be involved?
    • skeletal muscle
    • liver
    • heart
    • brain
  23. what is type I glycogen storage disorder also known as? and what is the enzyme deficiency?
    • von Gierke disease
    • glucose-6-phosphatase
  24. which organ does type 1 GSD affect mostly?
  25. what are the 3 main clinical features of type 1 GSD?
    • hepatomegaly
    • growth failure
    • hypoglycaemia
  26. 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
  27. 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
  28. what are the long term complications of type 1 GSD?
    • hyperlipidaemia
    • hyperuricaemia
    • hepatic adenomas
    • cardiovascular disease
  29. which systems of the body do MPS affect?
    • CNS
    • eyes
    • heart
    • skeletal system
  30. 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
  31. what is MPS1 known as?
    Hurler syndrome
  32. what are clinical features of Hurler syndrome?
    • coarse facial features
    • corneal opacities
    • hepatosplenomegaly
    • kyphosis
    • mental retardation
  33. how is diagnosis of MPS made?
    • identify enzyme defect
    • identify excretion in urine of major storage substances - GAG glycosaminoglycans
  34. what is Rx of MPS?
    bone marrow transplant if done early
  35. what is the inheritance of most MPS?
    auto recessive