EXAM #2: INHERITED METABOLIC DISORDERS Flashcards
When should a metabolic disorder be considered in a child?
1) All neonates with unexplained, overwhelming, or progressive disease after normal pregnancy
2) All kids with acute deterioration after routine illness
3) All kids with acidosis or hypoglycemia
What is the most common inheritance pattern of the inborn errors of metabolism?
Autosomal recessive
In obtaining a history, what is paramount when an inborn error of metabolism is suspected?
Diet history
What should you do if you suspect acute toxicity from an inborn error of metabolism?
Stop oral feeding
What is a red flag physical exam finding in a newborn?
Diaphoresis (newborns should NOT sweat)
What can grunting respirations in a child be a sign of?
Metabolic derangement/ acidosis
What is the differential for a seizure in a newborn/child?
1) Infection
2) CNS abnormality
3) Metabolic disorder
How are inborn metabolic errors worked up?
1) Electrolytes, glucose, ammonia
2) Blood, urine, CSF cultures
3) Head CT/MRI
What is the general rule of thumb regarding abx in a newborn?
Error on the side of giving abx vs. not
What is phenylalanine converted to?
Tyrosine
What enzyme converts phenylalanine to tyrosine?
phenylalanine hydroxylase
What is the result of the enzyme defect seen in classic PKU?
Autosomal recessive defect in liver phenylalanine hydroxylase that leads to:
- Increased phenylalanine
- Phenylketones
How is PKU treated?
1) Restrict Phe to 250-300mg per day
2) Lofenalac
What is malignant hyperphenylalaninemia?
Defect in coenzyme for phenylalanine hydroxylase
*Note that dietary Phe restriction will not improve sx.
What are the clinical manifestations of PKU?
1) Choking spells
2) Feeding difficulty
3) Vomiting
4) Abnormal neurological development i.e. autism like features
What do you need to remember about the dietary restrictions of PKU?
Maintain throughout life–esp. in pregnancy
What causes galactosemia?
Defect in galactose 1-phospate uridylyltransferase
What accumulates in galactosemia?
Galactose 1-phosphate
What are the clinical manifestations of galactosemia?
- Vomiting
- Diarrhea
- Hepatosplenomegaly (HSM)
- Jaundice
- Anemia
What are kids with galactosemia susceptible to?
Gram negative sepsis esp. E.coli
How is Galactosemia diagnosed?
- Red cell enzyme tests
- Urine with reducing substrate
How is Galactosemia treated?
1) No breast-feeding
2) No lactose/ cow’s milk
3) Switch to soy formula
What are the three major things to monitor for in kids with Galactosemia?
1) Developmental delay
2) Cataracts
3) Premature ovarian failure
What is MCAD?
Medium-chain acyl-CoA dehydrogenase deficiency
*Disorder of fatty acid oxidation
What should be avoided in MCAD?
Fasting
What is a typical presentation of MCAD?
Kid will fast all night, vomit in am, and then be comatose from hypoglycemia
How do you tell the difference between an organic acidemia and urea cycle disorder on blood gas?
pCO2 and HCO3 will be LOW in BOTH
*Organic= low pH; Urea cycle= high pH
