PKU Flashcards
What are some of the clinical features of untreated PKU?
developmental delay but only evident around 6 months (diagnosis is typically delayed b/c symptoms due not present at birth)
severe mental retardation, hyperactivity, hypertonia, seizures, microcephaly, EEG abnormalities
What are some of the cutaneous symptoms of untreated PKU?
- pigment dilution in hair, skin
- eczema
- musty odor
What is PKU caused by?
deficient phenylalanine hydroxylate which is responsible for converting phenylalanine to tyrosine
What is the inheritance mode of PKU?
autosomal recessive
Is phenylalanine essential or nonessential?
essential (ingested in diet)- so it can be treated with limited dietary intake
What are the breakdown products of phenylalanine? the ‘phenylketones’
phenylacetic acid, phenyl lactic acid, and phenylpyruvic acid (these are probably what is responsible for the toxic CNS effect caused by PKU- not the accumulation of phenylalanine)
What are some of the lab findings of patients with untreated PKU?
phenylketones in urine (which are not usually present) that are variable based on the type of PKU and age of patient,
odor in urine
plasma- elevated phenylalanine (normal
What is the major site for the action of phenylalanine hydroxlase?
the liver (although the main effects are the CNS)
What is the best way to prevent PKU advance?
the effects of PKU cannot be reversed so newborn screening is the best way to diagnosis early and prevent the CNS effects of PKU. Once you have a positive diagnosis, you can limit dietary Phe intake to mediate the effects/progression of the disease
What are the newborn screening requirements of PKU?
all newborns are required to be screened before discharge, all screened after 24 hrs of age and by 48 hrs at the latest
Are there abnormal cofactors associated with classical PKU?
No, they are normal
What are the signs of classical PKU?
most severe form
Phe >20mg% (all these patients are treated to
What are the signs of variant PKU?
10-20mg% Phe tyr normal, Phe variable cognitive impaired variable more likely to respond to BH4 therapy variable maternal PKU effect if untreated
all treated to
What are the signs of non-PKU hyperphenylalaninemia?
4-10mg% Phe tyr normal, Phe negative lower risk of cognitive impairment if untreated may respond to BH4 therapy maternal PKU effect unclear
most treated to
Newborn screening has shown that not all cases of elevated Phe are caused by PKU. What are some of the other potential causes?
hypertyrosinemia
immature liver
cofactor abnormalities
TPN (total parenteral nutrition)- nutrition by IV
