E–F

Edwards syndrome An AUTOSOMAL TRISOMYdisor-
der that results from a REPLICATION ERRORduring
cell division in which a GAMETE(sex cell) ends up
with two copies of CHROMOSOME18 instead of the
normal single copy (as haploid cells, gametes con-
tain one half the complement of chromosomes).
At fertilization the ZYGOTEthus ends up with three
instead of the normal two copies of chromosome
18, which ultimately produces multiple and life-
threatening congenital anomalies.
When all cells carry the extra chromosome 18),
the anomalies are so severe that the defect often is
lethal well before birth. Sometimes Edwards syn-
drome occurs as a mosaic trisomy disorder (some
but not all cells contain the third chromosome
18), which tends to produce milder though
nonetheless significant symptoms. Edwards syn-
drome occurs in about 1 in 5,000 live births in the
United States, 80 percent of which are females.
Researchers do not know whether Edwards syn-
drome affects females more often or if females are
more likely to survive beyond birth.
Children born with Edwards syndrome have
severe and complex physical deformities involving
multiple organs and systems that require exten-
sive medical care from the time of birth. Most also
have profound intellectual impairment arising
from malformations affecting the BRAINand NERV-
OUS SYSTEM. A KARYOTYPE confirms the diagnosis.
Fewer than 10 percent of infants born with
Edwards syndrome survive the first year after
birth; those who do require extensive, ongoing
medical care and developmental support. Survival
beyond five years is extremely rare.
Doctors often can diagnose Edwards syndrome
and other autosomal trisomy disorders before
birth, through prenatal screening methods such as
AMNIOCENTESISand CHORIONIC VILLI SAMPLING(CVS).

These methods retrieve cells from the FETUSfrom

which a geneticist can construct a karyotype.

Advanced maternal age (mother’s age over 40)

and the previous CONCEPTION of a child with

Edwards syndrome or another autosomal trisomy

disorder are the leading risks for Edwards syn-

drome. Whether done prenatally or after birth the

karyotype, which presents photomicrographic

images of the fetus’s or infant’s chromosomes,

provides definitive diagnosis.

CONGENITAL ANOMALIES

CHARACTERISTIC OF EDWARDS SYNDROME

facial deformities

fingers curled over one another in clenched fists

heart defects

kidney abnormalities

low, small ears

microcephaly (small head and BRAIN)

small MOUTHand cleft deformities

spina bifida

SYNDACTYLY

TALI PEDES(club foot)

See also AUTOSOME; CHROMOSOME DISORDERS; CON-

GENITAL ANOMALY; CONGENITAL HEART DISEASE; DOWN

SYNDROME; ETHICAL ISSUES IN GENETICS AND MOLECULAR

MEDICINE; GENETIC SCREENING; INHERITANCE PATTERNS;

MOSAICISM; PATAU’S SYNDROME; PRENATAL CARE.

ethical issues in genetics and molecular medicine

The questions and concerns that arise for physi-

cians and individuals in regard to the information

GENETIC SCREENING, GENETIC TESTING, and genetic and

molecular therapies. Though advances in genetics

have produced significant breakthroughs in under-

standing, diagnosing, and sometimes treating

health conditions that occur as a result of GENETIC

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