Congenital malformations - Edocr

60 PART II CENTRAL NERVOUS SYSTEM MALFORMATIONS
If the family history is completely unremarkable
in a sporadic case of holoprosencephaly,
the risk of recurrence is likely relatively low.
Some cases may represent new mutations of
autosomal dominant genes. The recurrence risk
is always greater than that faced by couples in
the general population, however, because of
the possibility of gonadal mosaicism for a dominant
gene mutation or because of the possibility
that a parent could be a nonexpressing carrier of
a dominant gene. High resolution ultrasonography
should be offered in subsequent pregnancies
for examination of the intracranial anatomy
and facial structures. Alobar holoprosencephaly
should be easily detectable in the midtrimester
of pregnancy by ultrasonography. 4 Semilobar
and lobar holoprosencephaly cannot be reliably
detected by prenatal ultrasound examination,
although the accompanying facial anomalies
may be detected. If a previous child with
holoprosencephaly has had a chromosome
anomaly, then prenatal chromosome analysis,
by chorionic villus sampling or amniocentesis,
should be offered.
REFERENCES
1. Muenke M and Gropman A. Holoprosencephaly
Overview. Available at: http://www.genetests.org.
Accessed March 11, 2006.
2. Hehr U, Gross C, Diebold U, et al. Wide phenotypic
variability in families with holoprosencephaly and a
sonic hedgehog mutation. Eur J Pediatr. 2004;163:
347–52.
3. Hahn JS, Plawner LL. Evaluation and management
of children with holoprosencephaly. Pediatr Neurol.
2004;31:79–88.
4. Joo GJ, Beke A, Papp C, et al. Prenatal diagnosis,
phenotypic and obstetric characteristics of holoprosencephaly.
Fetal Diagn Ther. 2005;20:161–6.