The patches are usually harmless,
although occasionally they result in a
cancerous change in the affected tissue.
If the condition persists, the patches
are removed under local anaesthesia
and tissue is examined microscopically
for signs of malignant change. (See also
mouth cancer;vulva, cancer of.)
leukorrhoeaSee vaginal discharge.
leukotriene receptor antagonistsA
group of antiallergydrugs, such as mon-
telukastand zafirlukast, used to prevent
symptoms of mild to moderate asthma.
The drugs work by blocking the effects
of leukotrienes – naturally occurring sub-
stances released in the lungs during an
allergic reaction.
Because they are not bronchodilator
drugs, and will not relieve an existing
attack, they are usually used with bron-
chodilators and inhaled corticosteroids
to reduce the frequency of attacks.
Side effects include gastrointestinal
disturbances and headache. Skin and
hypersensitivity reactions may also occur.
levamisole An anthelmintic druggiven
by mouth in a single dose to eliminate
roundworminfestation. Side effects of
levamisole are rare but can include mild
nausea or vomiting.
levodopaA drug used to treat Parkin-
son’s disease. Side effects include nausea,
vomiting, nervousness, and agitation.
levonorgestrelA progestogen drug used
in some oral contraceptives.
levothyroxineA synthetic version of
the thyroid hormonethyroxine, used to
treat hypothyroidism. Side effects, such
as rapid heartbeat and tremor, may occur
if the initial dose is too high.
LHThe abbreviation for luteinizing hor-
mone.
LH-RHThe abbreviation for luteinizing
hormone-releasing hormone.
libidoSexual desire. Loss of libido is a
symptom of many physical illnesses and
of depression, drug abuse, and alcohol
abuse. (See also sexual desire, inhibited.)
liceSmall, wingless insects that feed
on human blood. There are 3 species:
PEDICULUS HUMANUS CAPITIS(the head
louse), PEDICULUS HUMANUS CORPORIS(the
body louse), and PHTHIRUS PUBIS(the crab,
or pubic, louse). All have flattened bod-
ies and measure up to 3 mm across.
Head lice live on the scalp and their
bite causes intense itching. They are
spread by direct contact. Their tiny eggs
(nits) attach to hairs close to the scalp.
Body lice live and lay eggs on clothing
next to the skin. They can transmit epi-
demic typhusand relapsing fever. Crab
lice live in pubic hair or, more rarely, in
armpits, beards, or eyelashes; they are
usually transmitted during sexual contact
(see pubic lice). Various preparations
can be applied to kill lice and eggs.
lichenificationThickening and harden-
ing of the skincaused by repeated
scratching, often to relieve the intense
itching of disorders such as atopic
eczemaor lichen simplex.
lichen planusA common skindisease
of unknown cause that usually affects
middle-aged people. Small, shiny, in-
tensely itchy, pink or purple raised spots
appear on the skin of the wrists, fore-
arms, or lower legs. There is often a lacy
network of white spots covering the
inside lining of the cheeks. The disease
is treated with topical steroid drugs.
lichen sclerosus et atrophicusA
chronic skin condition of the anogenital
area. The skin is scarred and white, and
the anatomy of areas such as the vagi-
nal opening or the foreskin may become
distorted. Treatment is with potent top-
ical steroid drugs.
lichen simplexPatches of thickened,
itchy, sometimes discoloured skin, due
to repeated scratching. Typical sites are
the neck, wrist, elbow area, and ankles.
Lichen simplex is most common in
women and is often stress-related. Treat-
ment is with oral antihistamine drugsand
creams containing corticosteroid drugs,
and may also involve addressing any
underlying stress or anxiety.
lid lagA momentary delay in the nor-
mal downward movement of the upper
eyelids that occurs when the eye looks
down. Lid lag is a characteristic feature
of thyrotoxicosis, and usually occurs in
conjunction with exophthalmos.
lidocaineA local anaesthetic (see an-
aesthesia, local) used to numb tissues
before minor surgical procedures, and
as a nerve block.
life expectancyThe number of years a
person can expect to live. Life expectancyLEUKORRHOEA LIFE EXPECTANCY
L