Fetal Hyperphenylalaninemia Syndrome
with hyperphenylalaninemia may give birth to neonates with microcephaly.
Phenylalanine levels are higher in the fetus than in the mother (at a
ratio of about 3:2). Mothers with hyperphenylalaninemia may have a history
of phenylketonuria or may be unaware of their condition. In addition to
microcephaly, neonates with hyperphenylalaninemia syndrome may have: a
round face with prominent glabella and epicanthal folds, short palpebral
fissures, poorly developed but long philtrum, thin upper lip, and small
upturned nose. Cardiac anomalies may be present. These characteristics
are not present in all neonates with intrauterine exposure to hyperphenylalaninemia;
therefore, fetal hyperphenylalaninemia syndrome should be considered in
all neonates with unexplained microcephaly. The diagnosis is confirmed
by finding an elevated phenylalanine level in maternal blood. Future pregnancies
should be closely monitored. A maternal phenylalanine level should be
kept between 120 and 360 mmol/L (2 to 6 mg/dL) before conception and during
pregnancy. Women with elevated phenylalanine levels should also take multivitamins
including B12 and folic acid.
exposure during early pregnancy is a common cause of mental retardation.
The earlier the exposure and the larger the amount of alcohol ingested,
the more likely it is for fetal alcohol syndrome to occur. Microcephaly
is one of the most consistent features in fetal alcohol syndrome in neonates.
In addition, neonates are shorter and thinner than normal and have characteristic
facial features. The characteristic facial features are short palpebral
fissures, epicanthal folds, midfacial hypoplasia, low nasal bridge with
short upturned nose, long hypoplastic philtrum, and a long upper lip with
a narrow vermilion border. Limb abnormalities occur less often than facial
abnormalities. The limb abnormalities include palmar crease abnormalities
and joint contractures.