shuntAn abnormal or surgically created
passage between two normally uncon-
nected body parts.
Shy–Drager syndromeA rare degener-
ative disorder of unknown cause that
progressively damages the autonomic
nervous system. It begins gradually at
age 60–70 and is more common in men.
Symptoms include dizziness and fainting
due to postural hypotension, urinary in-
continence, impotence, reduced ability to
sweat, and parkinsonism. The condition
eventually leads to disability, and some-
times premature death. There is no cure
or means of slowing degeneration, but
many symptoms are relieved by drugs.
SIADHThe abbreviation for syndrome of
inappropriate antidiuretic hormone (se-
cretion), associated with certain lung or
brain disorders and some types of cancer.
Siamese twinsSee twins, conjoined.
sibling rivalryA term that describes
the intense competition that sometimes
occurs between siblings.
sibutramineA centrally acting appetite
suppressantdrug used to treat obesity
in people who have not responded to
other methods of weight loss, such as
dieting. Common side effects include
constipation, dry mouth, and hyperten-
sion. People taking this drug should
have regular follow-ups and have their
blood pressure and pulse monitored.
sick building syndromeA collection
of symptoms reported by some workers
in office buildings. Symptoms include
loss of energy, headaches, and dry, itch-
ing eyes, nose, and throat. The cause is
unknown, but various factors are invol-
ved, including air conditioning, passive
smoking, lack of natural ventilation and
light, and psychological factors.
sickle cell anaemiaAn inherited blood
disease in which the red blood cells con-
tain haemoglobin S, an abnormal type of
haemoglobin. This crystallizes in the cap-
illaries, making red cells sickle-shaped
and fragile, and leading to haemolytic
anaemia. The abnormal cells are unable
to pass easily through tiny blood vessels.
The blood supply to organs is blocked
intermittently, causing sickle cell crises.
The disease affects mainly black people.
Symptoms usually appear after age 6
months, often beginning with painful
swelling of the hands and feet. Chronic
haemolytic anaemia causes fatigue,
headaches, shortness of breath on exer-
tion, pallor, and jaundice. Sickle cell
crises start suddenly; they are sometimes
brought on by an infection, cold wea-
ther, or dehydration, but may also occur
for no apparent reason. The sufferer may
experience pains (especially in the
bones), blood in the urine (from kidney
damage) or damage to the lungs or intes-
tines. If the brain is affected, seizures,a
stroke, or unconsciousness may result.
In some affected children, the spleen
enlarges and traps red cells at a particu-
larly high rate, causing a life-threatening
form of anaemia. After adolescence, the
spleen usually stops functioning, increas-
ing the risk of infection in those affected.
Diagnosis is made from examination of
a blood smear and electrophoresis. Sup-
portive treatment may include folic acid
supplements, and penicillin and immu-
nization to protect against infection.
Life-threatening crises are treated with
intravenous infusionsof fluids, antibiotics,
oxygen therapy, and analgesic drugs. If
the crisis still does not respond, an
exchange blood transfusionmay be per-
formed. This may be done regularly for
people who suffer frequent severe crises.
sick sinus syndromeAbnormal func-
tion of the heart’s sinoatrial nodethat
leads to episodes of bradycardia(slow
heart-rate), alternating bradycardia and
tachycardia(fast heart-rate), or very short
episodes of cardiac arrest. The cause is
usually coronary artery disease, but may
be a cardiomyopathy.Symptoms may
include lightheadedness, fainting, and
palpitations. The diagnosis is confirmed
by a 24-hour ECGrecording. Treatment
is usually by antiarrhythmic drugsand
the fitting of an artificial pacemaker.
side effectA reaction or consequence of
medication or therapy that is additional
to the desired effect. The term usually
refers to an unwanted or adverseeffect,
usually following a normal dose, rather
than the toxic effects, of a drugoverdose.
siderosisAny of a variety of conditions
in which there is too much iron in the
body. (See also haemosiderosis.)
SIDSAn abbreviation for sudden infant
death syndrome.SHUNT SIDS
S