POLYMERASE CHAIN REACTION
PORPHYRIA
causing abdominal pain, breathlessness,
nausea, and vomiting, and leg swelling.
Premature labour may result.
The condition is usually evident from
a physical examination, but
ultrasound
scanning
may be needed. In mild cases,
only rest is needed. In more severe
cases, amniotic fluid may be withdrawn
using a needle. In late pregnancy,
induc-
tion of labour
may be performed.
polymerase chain reaction (PCR) A
method of rapidly copying
DNA
se-
quences so that they can be analysed.
polymyalgia rheumatica An uncom-
mon disease of elderly people, marked
by pain and stiffness in the muscles of
the hips, thighs, shoulders, and neck.
Symptoms are worse in the mornings.
The cause is unknown, but the condition
may be associated with
temporal arteri-
tis.
It is unusual before the age of 50.
The diagnosis is often difficult to con-
firm and is based on the patient's history,
a physical examination, and blood tests
(including an
ESR
). If temporal arteritis
is suspected, a
biopsy
may be performed
on an artery at the side of the scalp.
Corticosteroid drugs
usually improve
the condition within a few days.
polymyositis A rare disease in which
the muscles are inflamed and weak.
polymyxins A group of
antibiotic drugs
derived from the bacterium
bacillu s
polymyxa
.
Polymyxins, which include
colistin
, are commonly given to treat
eye, ear, and skin infections.
polyp A growth that projects, usually on
a stalk, from the lining of the nose, the
cervix, the intestine, the larynx, or any
other
mucous membrane.
Some types
are liable to develop into cancer, and
are surgically removed.
polypeptide A compound consisting of
many
peptides.
polypharmacy The practice of pres-
cribing several drugs to
1
person at the
same time.
polyposis, familial A rare, inherited dis-
order, also known as polyposis coli, in
which many
polyps
are present through-
out the gut, but mainly in the colon. If
not treated, cancer of the colon (see
colon, cancer of
) is almost certain to
develop. The polyps may appear from
age
10
. They may cause bleeding and
diarrhoea; however, there are often no
symptoms until cancer has developed.
The polyps are detected by
colonoscopy.
Since there is a 50 per cent chance
that children of an affected person will
inherit the disease, medical surveillance
is necessary from around the age of
12
.
Individual polyps may be cauterized (see
cauterization).
The high risk of developing
cancer often means that a
colectomy
and an
ileostomy
are performed.
polyunsaturated fats Fats (see
fats and
oils
) with with relatively few hydrogen
atoms in their chemical structure. Poly-
unsaturated fats tend to protect against
cardiovascular disease.
polyuria See
urination, excessive
.
PoM The abbreviation for
prescription-
only medicine.
pompholyx An acute form of
eczema
in
which itchy blisters form on the palms
and/or soles. The condition, also called
dyshydrotic eczema, is sometimes due
to an allergic response. Rarely, it is asso-
ciated with
ringworm.
Treatment is with
an astringent or with topical application
of a
corticosteroid drug
.
pons The middle part of the
brainstem.
pore A tiny opening, usually in the skin.
porphyria Any of a group of uncom-
mon and usually inherited disorders
caused by the accumulation of sub-
stances
called
porphyrins.
Sufferers
often have a rash or blistering brought
on by sunlight, and certain drugs may
cause abdominal pain and nervous sys-
tem
disturbances.
Porphyrins
are
formed in the body during the manufac-
ture of haem (a component of
haemo-
globin
). A block in this manufacture
causes a build-up of porphyrins. Such
blocks are the result of various
enzyme
deficiencies, which are
genetic disorders.
Porphyria may also be due to poisoning.
There are
6
types of porphyria. Acute
intermittent porphyria usually appears
in early adulthood, causing abdominal
pain, and often limb cramps, muscle
weakness, and psychiatric disturbances.
The patient's urine turns red when left
to stand.
Barbiturate drugs, phenytoin,
oral contraceptives
,
and
tetracyclines
precipitate attacks.
Variegate porphyria has similar effects
but also causes blistering of sun-exposed
P
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