Endo...Q - maryam2009

[ArchivalUser]

A 20-year old female who is 2 months pregnant remembers that she had
phenylketonuria (PKU) as a child and required a special diet. Tests
confirm markedly elevated maternal serum levels of phenylalanine and
phenylacetic acid. Genetic studies have not been performed on the
father. What should the physician tell the parents regarding the
welfare of the child?
A. Childhood phenylalanine restriction is sufficient to protect the health of her child.
B. Further information is required to ascertain if the fetus is at risk.
C. The fetus is at no health risk if it is heterozygous for the PKU gene.
D. The fetus is at no health risk if phenylalanine levels are normalized by the third trimester.
E. The mother's hyperphenylalaninemia may have already harmed the fetus.

[ArchivalUser]

EEEEE

[ArchivalUser]

EE

[ArchivalUser]

Thecorrect answer is E.

Phenylalanine crosses the placenta and, if maternal serum levels are elevated, acts as a teratogen to the developing fetus. This condition is known as maternal PKU. Although the mother can fare well with substantial elevations in serum phenylalanine concentration, the children born to such women are usually profoundly retarded and may have multiple birth defects.
Although dietary modifications (choice A) can prevent the neurological and dermatologic manifestations of PKU in a child, the fetus is still at risk from maternal PKU.
Further information regarding the cause of this woman's hyperphenylalaninemia (choice B) is not needed, since the fetus is exposed to teratogenic levels of phenylalanine.
Children born to mothers with untreated PKU develop maternal PKU even if they are heterozygous for the PKU gene (choice C). Fetal phenylalanine hydroxylase cannot compensate for the high maternal levels of phenylalanine.
The critical period in development during which teratogenic materials affect the growing organs is between the 3rd and 8th weeks of gestation. By the end of the 2nd month (compare with choice D), the damage caused by the maternal PKU has already occurred.

[ArchivalUser]

@Maryam, what's wrong with choice B? I was thinking the first thing you will like to ascertain is the fathers PKU genotype. Given that PKU is autosomal recessive, to tell if the infant will have been infected, we need at least to know the status of the father. Don't you think so?

[ArchivalUser]

if maternal serum levels of phenylalanineis elevated,....it acts as a teratogen to the developing fetus. ,.... the child is already exposed to the teratogen and may have already harmed the fetus......the fetus is at risk and we don't need to get furture information

[ArchivalUser]

** Further