Bma Illustrated Medical Dictionary

pilonidal sinusA pit in the skin, often

containing hairs, in the upper part of

the buttock cleft. The cause is probably

hair fragments growing inwards. Al-

though usually harmless, infection may

occur, causing recurrent, painful ab-

scesses. If a sinus is infected, a wide

area around it is surgically removed.

Recurrence of infection is common, and

plastic surgery is sometimes required.

pimozideAn antipsychotic drugalso

used to treat Gilles de la Tourette’s syn-

drome. Pimozide may cause sedation, dry

mouth, constipation, and blurred vision.

pimpleA small pustuleor papule.

pindololA beta-blocker drugused to

treat angina pectorisand hypertension.

Possible side effects are typical of other

beta-blocker drugs, except that pindolol

is less likely to cause bradycardia.

pineal glandA tiny, cone-shaped struc-

ture deep within the brain, whose sole

function appears to be the secretion of

melatoninin response to changes in light.

pingueculaA small, noncancerous, yel-

lowish spot on the conjunctivaover the

white of the eye. They are common in

elderly people, and may be removed for

cosmetic reasons.

pink-eyeSee conjunctivitis.

pinnaThe fleshy part of the outer ear,

consisting of a flap of cartilage and skin.

It is also called the auricle.

pins-and-needlesA tingling or prickly

feeling in an area of skin that is usually

phyto- A prefix meaning of plant origin.
phytomenadioneA form of vitamin K.
phyto-oestrogensOestrogensthat oc-
cur naturally in plants.
pia materThe innermost of the 3 mem-
branes of the meninges.
picaA craving to eat non-food substan-
ces such as earth or coal. Pica is common
in early childhood and may occur during
pregnancy. It may also occur in nutri-
tional or iron-deficiency disorders, and
in severe psychiatric disorders.
Pickwickian syndromeAn unusual dis-
order characterized by extreme obesity,
shallow breathing, and sleep apnoea. The
cause is unclear. Symptoms usually im-
prove with weight loss.
PIDSee pelvic inflammatory disease.
pigeon toesA minor abnormality in
which the leg or foot is rotated, forcing
the foot and toes to point inwards. The
condition is common in toddlers.
pigmentationColoration of the skin,
hair, and irisof the eyes by melanin. The
more melanin present, the darker the
coloration.Blood pigments can also
colour skin (such as in a bruise).
There are many abnormalities of pig-
mentation. Patches of pale skin occur in
psoriasis, pityriasis alba, pityriasis versi-
color, and vitiligo. Albinism is caused by
generalized melanin deficiency. Phenyl-
ketonuriaresults in a reduced melanin
level, making sufferers pale-skinned and
fair-haired. Areas of dark skin may be
caused by disorders such as eczemaor
psoriasis, pityriasis versicolor, chloasma,
or by some perfumes and cosmetics
containing chemicals that cause photo-
sensitivity. Permanent areas of deep
pigmentation, such as freckles and moles
(see naevus), are usually due to an
abnormality of melanocytes. Acanthosis
nigricansis characterized by dark patch-
es of velvet-like, thickened skin. Blood
pigments may lead to abnormal colour-
ing. Excess of the bile pigment bilirubin
in jaundiceturns the skin yellow, and
haemochromatosisturns the skin bronze.
pilesA common name for haemorrhoids.
pill, contraceptiveSee oral contracep-
tives.
pilocarpineA drug used to treat glau-
coma. It may initially cause blurred vision,
headache, and eye irritation.

PHYTO- PINS-AND-NEEDLES

P

PINEAL GLAND

Pineal gland

Corpus Cerebellum

callosum

Pituitary

gland

Cerebrum of brain