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Gyrus Daily Questions; Pediatrics #42

1K views 6 replies 6 participants last post by  cingulate.gyrus 
#1 ·
A 5-week-old male presents with poor feeding, poor growth, a peculiar odor, hypertonia, and hyperactive reflexes. He is afebrile. History reveals no problems with labor and delivery and early hospital discharge at 24 hours of age.
He has not seen a physician since that time. Which of the following is the most likely etiology of this infant’s condition?

(A) sepsis
(B) pyloric stenosis
(C) overfeeding
(D) phenylketonuria (PKU)
(E) hypothyroidism
 
#7 ·
Answer is D

Classic phenylketonuria results from the lack of, or near complete lack of, phenylalanine hydroxylase. Impaired metabolism of the common essential amino acid phenylalanine to tyrosine leads to build-up of phenylpyruvic acid and phenylethylamine. These products as well as excess phenylalanine lead to central nervous system damage.

Newborns are routinely screened for PKU. The screening is performed by collecting blood spots on filter paper at the time of discharge from the hospital to home and before 7 days of life. Infants discharged at less than 24 hours of age should have the screening test repeated prior to 14 days of life. Unfortunately, this baby did not have adequate newborn screening. For PKU, presymptomatic diagnosis allows control of the disease through control of the diet of the infant. Though further CNS damage can be prevented in this case with dietary control, the signs and symptoms this baby displays are, for the most part, irreversible. The other choices are not associated with this constellation of symptoms.
 
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