Down syndrome have atrial or ventricular septal
defects (openings or holes in the septum, or wall,
between the chambers of the heart). About half
also have impaired vision (notably, congenital
cataracts and AMBLYOPIA) and partial to complete
HEARING LOSS. About 10 percent have malforma-
tions of the intestines that require surgical correc-
tion. All individuals with Down syndrome have
some intellectual impairment. Mild to moderate
intellectual impairment is most common. Some
children who have Down syndrome do well in
regular classes in school and grow up to be capa-
ble of independent living.
Doctors often can diagnose Down syndrome
and other autosomal trisomy disorders before
birth using prenatal screening methods such as
blood tests, ULTRASOUND, AMNIOCENTESIS, and CHORI-
ONIC VILLI SAMPLING(CVS). These methods retrieve
cells from the FETUSfrom which a geneticist can
construct a KARYOTYPE, which presents photomi-
crographic images of the fetus’s or infant’s chro-
mosomes. Advanced maternal age (mother’s age
over 40) and the previous conception of a child
with Down syndrome or another autosomal tri-
somy disorder are the leading risks for Down syn-
drome. Whether done prenatally or after birth the
karyotype provides definitive diagnosis.
Treatment Options and Outlook
There are no specific treatments for Down syn-
drome. Because children who have Down syn-
drome are more susceptible to INFECTION, they
often need more medical care while growing up.
There is a high correlation between early-onset
ALZHEIMER’s DISEASE and adults who have Down
syndrome. Typically men who have Down syn-
drome are sterile, though women who have
Down syndrome may be fertile and can become
pregnant. Their risk for conceiving a child with
Down syndrome is very high, however, and doc-
tors strongly recommend GENETIC COUNSELING.
About 350,000 Americans live with Down syn-
drome. Because Down syndrome is the mildest of
the survivable trisomy disorders and because it
can occur in a mosaic rather than a complete pres-
entation, some people who have it are able to lead
relatively independent and productive lives, living
into their mid-50s or beyond. Early treatment for
the anomalies common with Down syndrome,
such as septal defects, and ongoing care for other
health conditions, such as HYPOTHYROIDISM and
VISION IMPAIRMENT, have greatly improved both
health and QUALITY OF LIFEfor people who have
Down syndrome.Risk Factors and Preventive Measures
Down syndrome occurs as a replication error that
does not appear to be preventable, though recent
research suggests that folic acid supplementation
beginning before conception and extending
through PREGNANCY, such as obstetricians recom-
mend for preventing NEURAL TUBE DEFECTS, may
reduce the risk for Down syndrome. Older
women, who have a higher risk of conceiving a
child with Down syndrome, may opt for genetic
testing early in pregnancy to determine whether
the fetus has the trisomy 21 GENOTYPE. Knowing
allows the woman to make appropriate plans and
decisions regarding the pregnancy and potential
care needs of the child.CONGENITAL ANOMALIES
CHARACTERISTIC OF DOWN SYNDROME
AMBLYOPIA atrial septal defect
BOWEL ATRESIA broad, short neck
congenital cataracts developmental delays
flat, upwardly slanting eyes HEARING LOSS
intellectual impairment rounded face
short stature small ears
small hands and short fingers small NOSEand MOUTH
ventricular septal defectSee also AUTOSOME; CATARACT; CONGENITAL ANOM-
ALY; CHROMOSOME DISORDERS; CONGENITAL HEART DIS-
EASE; EDWARDS SYNDROME; ETHICAL ISSUES IN GENETICS
AND MOLECULAR MEDICINE; GENETIC SCREENING; INHERI-
TANCE PATTERNS; MOSAICISM; PATAU’S SYNDROME; PRE-
NATAL CARE.Down syndrome 123