called periarteritis nodosa. Areas of arter-
ial wall become inflamed, weakened, and
The severity of the
condition depends on the arteries that
are affected and how much they are
weakened. The cause seems to be an
triggered by exposure to the
virus. It is most common in adults and
affects men more than women.
Early symptoms of polyarteritis nodosa
include fever, aching muscles and joints,
general malaise, loss of appetite and
weight, and, sometimes, nerve pain.
There is also
If the coronary
arteries are affected,
may occur. Many patients suffer
abdominal pain, nausea, vomiting, diar-
rhoea, and blood in the faeces.
Diagnosis is made by
. Large doses of
and in some cases
may allow survival for at least 5 years.
Without treatment, few patients survive
for this length of time.
polycystic kidney See
polycystic ovary See
polycythaemia A condition in which
increased production of red
leads to an unusually large number of
them in the blood. This condition is
usually caused by another disorder or
and is called secondary
polycythaemia. If it occurs for no appar-
ent reason, it is called polycythaemia
vera or primary polycythaemia.
Secondary polycythaemia occurs natu-
rally at high altitudes due to the
reduced oxygen level. It can also result
from a disorder that impairs the oxygen
supply to the blood, or can be secon-
or some kidney
disorders. Descending to sea level, or
effective treatment of an underlying dis-
order, returns the blood to normal.
Polycythaemia vera is a rare disorder
that mainly affects people over 40. The
large number of red blood cells causes
increased volume and thickening of the
blood, which may lead to headaches,
blurred vision, and
may also be flushed skin, dizziness, night
sweats, and widespread itching. The
is often enlarged. Possible com-
plications include a tendency to bleed
easily or to form blood clots;
or acute leukaemia (see
Diagnosis is made from a physical
and by rul-
ing out other causes. Treatment is by
, sometimes in combination
an ticancer dru gs
or with radioactive
phosphorus. This enables most patients
to survive for 10-15 years.
A birth defect in which
there is an excessive number of fingers
or toes. The extra digits may be fully
formed or they may be fleshy stumps.
Polydactyly often runs in otherwise nor-
mal families; however, it may also occur
as part of
or other congenital syndromes.
polydipsia Persistent excessive thirst
surrounding the fetus during pregnancy.
It occurs in about 1 in 250 pregnancies
and often has no known cause. The con-
dition sometimes occurs if the fetus has
a malformation that makes normal swal-
lowing impossible, or if the pregnant
amniotic fluid usually accumulates in
nd half of pregnancy, producing
symptoms from about week 32. The main
symptom is abdominal discomfort. Other
possible symptoms are breathlessness
and swelling of the legs. The uterus is
larger than would usually be expected.
Occasionally, fluid accumulates rapidly,