PICKWICKIAN SYNDROME
P
P ic k w ic k ia n s y n d ro m e
An uncommon disorder characterized
by extreme
o b e s it y
,
shallow breathing,
excessive
sleepiness,
and
o b s tru c t iv e
s le e p a p n o e a
.
Pickwickian syndrome is of
unknown cause. The symptoms usually
improve with weight loss; specific treat-
ment for sleep apnoea may be required.
PID
The abbreviation for
p e lv ic in fla m m a to ry
d is e a s e
.
p ie b a ld is m
A rare
g e n e t ic d is o r d e r
in w hich a patchy
absence of the dark pigment
m e la n in
results in areas of skin and sometimes
hair that lack pigmentation. In many
cases, there is a white panel in the cen-
tre of the face, which may include the
hair and eyebrows as well as the skin.
Piebaldism shows an autosomal domi-
nant pattern of inheritance.
p ie rc in g
See
e a r p ie r c in g
.
P ie rre R o b in ’s s y n d ro m e
A disorder causing abnormalities of the
lower jaw and throat. The condition
may occur by itself, or may be associat-
ed with other problems. It is
c o n g e n it a l
(present at birth).
The main structural malformations are
micrognathia (an abnormally small lower
jaw) and cleft palate (or an unusually
arched palate). Functional defects include
a tendency for the tongue to fall back-
wards into the throat, causing breathing
difficulty and a tendency to choke.
Affected babies may have difficulty in
feeding. Micrognathia may disappear as
the child grows, but cleft palate and air-
way obstruction may require surgery.
p ig e o n to e s
A m inor abnormality in w hich the leg
or foot is rotated, forcing the foot and
toes to point inwards. Although the
condition occurs commonly in tod-
dlers, it has usually corrected itself by
the time the child is seven years old.
p ig m e n ta tio n
Coloration of the skin, hair, and
ir is
of
the eyes by
m e la n in
,
a brown or black
pigment produced by cells called mel-
anocytes. The more melanin, the darker
the coloration (the amount produced is
determined by heredity and exposure to
sunlight).
Blood
pigments
can
also
colour skin (as in a bruise).
There are many defects of pigmenta-
tion, w hich may cause abnormally pale
or dark skin, or may produce areas of
discoloured skin.
REDUCED PIGMENTATION
Patches of pale skin occur in the skin dis-
orders
p s o r ia s is
,
p it y ria s is a lb a
,
and
p ity -
ria s is v e rs ic o lo r
;
these disorders cause skin
scales to flake off, resulting in a loss of
melanin. In
v itilig o
,
areas of skin stop pro-
ducing melanin.
The rare genetic disorder
a lb in is m
is
caused by a generalized deficiency of
melanin, and results in very pale skin
and white hair. Another genetic condi-
tion,
p h e n y lk e t o n u ria
,
results in a re-
duced level of melanin, making suffer-
ers of the condition more pale-skinned
and fair-haired than all the other mem-
bers of their family.
INCREASED PIGMENTATION
Areas of dark skin may appear tem-
porarily following
disorders such as
e c z e m a
or psoriasis, pityriasis versicolor,
or
c h lo a s m a
(development
of
dark
patches on the face due to hormonal
changes). Such areas of dark pigmenta-
tion may also appear after the use of
perfumes
and
cosmetics
containing
chemicals that cause
p h o t o s e n s it iv it y
.
Permanent areas of deep pigmenta-
tion, such as freckles, moles, or some
types of naevi (see
n a e v u s
), are usually
due to an abnormality in some of the
melanocytes.
A c a n t h o s is n ig r ic a n s
,
a con-
dition that may be either inherited or
acquired, is characterized by dark patches
of velvetlike, thickened skin. Darkening
of the skin that is unrelated to sun
exposure may occur in certain horm on-
al disorders, such as
A d d is o n ’s d is e a s e
and
C u s h in g ’s s y n d ro m e
.
ABNORMAL COLORATION
Some
forms
of abnormal
colouring
result from excessive levels of certain
pigments or other substances in the
blood. An excess of the bile pigment
bilirubin in
ja u n d ic e
turns the skin yel-
low, and an excessive blood level of iron
in
h a e m o c h ro m a to s is
turns
the
skin
bronze. Discoloration may also be caused
by an abnormal collection of blood ves-
sels, as in a
h a e m a n g io m a
,
or may occur
temporarily in a bruise, w hen blood
leaks from ruptured vessels and collects
under the skin.
p ile s
A common name for
h a e m o r r h o id s
.
p ill, c o n tra c e p tiv e
See
o ra l c o n tra c e p t iv e s
.
p ilo c a rp in e
A drug used in the form of eye-drops to
treat
g la u c o m a
(raised pressure in the
eyeball). Pilocarpine may initially cause
blurred vision, headache, and eye irrita-
tion. In tablet form, the drug is used to
treat
d r y m o u th
due to
S jo g r e n ’s s y n d ro m e
or
ra d io t h e ra p y
to the head and neck.
p ilo n id a l s in u s
A pit in the skin, often containing hairs,
in the upper part of the buttock cleft.The
cause is probably hair fragments grow-
ing inwards. Although the condition is
usually harmless, infection may occur,
causing recurrent, painful abscesses.
If a pilonidal sinus is infected, the
sinus and a wide area around it w ill
be surgically removed. The resulting
wound w ill usually be left open to allow
slow healing from the skin layers below.
Recurrence of infection is common, and
plastic surgery is sometimes required.
p im o z id e
An
a n tip s y c h o t ic d ru g
also used to treat
G ille s d e la T o u re tte ’s s y n d r o m e
.
Pimozide
may cause sedation, dry mouth, consti-
pation, and blurred vision.
p im p le
A small
p u s t u le
or
p a p u le
.
p in d o lo l
A
b e t a - b lo c k e r d ru g
used to treat
a n g in a
p e c t o r is
(chest pain due to inadequate
blood supply to the heart) and
h y p e rt e n -
s io n
(high blood pressure). Possible side
effects are typical of other beta-blocker
drugs, except that pindolol is less likely
than some others to cause
b ra d y c a rd ia
(abnormally slow heartbeat).
p in e a l g la n d
A tiny, cone-shaped structure deep within
the brain.The pineal gland is situated just
below the back of the corpus callosum,
the band of nerve fibres that connects the
two halves of the cerebrum (the topmost,
and largest, area of the brain).
The sole function of the gland appears
to be the secretion of the hormone
m e la -
to n in
in response to changes in light. The
amount of melatonin secreted varies over
a
24
-hour cycle, being greatest at night.
Hormone secretion is thought to be con-
trolled through nerve pathways from the
retina in the eye; a high light level seems
to inhibit secretion. The exact function of
melatonin is not understood, but it may
help to synchronize circadian (
24
-hour)
and other
b io rh y t h m s
.
608
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