Inborn Errors of Metabolism

Question 1

what are the majority of congenital metabolic disorders due to?

Answer 1

mutation of a single gene, causing a defect in the patient’s metabolism

Question 2

part of a larger group of inherited metabolic disorders called hyperphenylalaninemia, characterized by high blood levels of phenylalanine

Answer 2

PKU

Question 3

what causes the mousy odor in PKU?

Answer 3

phenylpyruvic acid in urine

Question 4

what defect exists in PKU?

Answer 4

defect in liver enzyme, phenylalanine hydroxylase

Question 5

what is the pathophysiology of PKU?

Answer 5

defect in phenylalanine hydroxylase
turns phenylalanine into phenylpyruvic acid instead of tyrosine

Question 6

what symptoms should we look out for in an infant, which will encourage consideration of inborn errors? (4)

Answer 6

unexplained failure to thrive
V/D, feeding difficulties
jaundice/hepatomegaly
irritability, hyperactivity, lethargy, coma

Question 7

intellectual disability, seizures, microcephaly, hypopigmentation, eczema, and mousy odor all indicate?

Answer 7

untreated PKU

Question 8

what diagnostic confirms the presence of inborn errors of metabolism?

Answer 8

genetic screening

Question 9

when is PKU screening done?

Answer 9

right after birth

Question 10

what 3 results can diagnose a patient with PKU?

Answer 10

high plasma phenylalanine
low plasma tyrosine
hydroxyphenylacetic acid in urine

Question 11

what is the goal in the management of PKU?

Answer 11

reduce serum phenylalanine to 3-8

Question 12

what is the treatment for PKU? (4)

Answer 12

low phenylalanine diet

supplement tyrosine in diet

adequate calorie intake

phenylalanine-free formula for supplemental support of vit/minerals

Question 13

what can proper nutritional management of PKU eliminate or reduce? (2)

Answer 13

intellectual disability
failure to thrive