mild bleaching action that reduces pigmentation
in the areas of application. Cosmetic procedures
such as dermatologist-performed chemical peel,
hydroquinone application (a bleaching agent), or
LASER SURGERYcan diminish or eliminate lentigines
and other blemishes on the face.
See also SKIN SELF-EXAMINATION; SUNBURN; SUN
PROTECTION.
lesion A generalized term for any abnormal
growth. Lesions can result from injury, disease, or
surgery. Some lesions are malignant (cancerous)
though most lesions are benign (noncancerous).
Numerous types of lesions affect the SKIN. Their
characteristics help define and diagnose disorders
and conditions of the skin as well as systemic dis-
orders that manifest dermatologic symptoms.
COMMON TYPES OF SKIN LESIONS
ACHROCHORDON ANGIOMA basal cell
BIRTHMARK BLISTER carcinoma
BULLA DERMATOFIBROSIS KELOID
LENTIGINES MACULE malignant
NEVUS NODULE melanoma
PAPILLOMA PAPULE plaque
PUSTULE SCALE SCAR
squamous cell TELANGIECTASIS ulcer
carcinoma VESICLE WHEAL
See also DERMATITIS; PLAQUE, SKIN; PSORIASIS; RASH;
SKIN CANCER.
lice See PEDICULOSIS.
lichen planus A common condition affecting the
SKINthat appears as small, shiny, reddish purple
(violaceous) bumps that itch, sometimes intensely.
The bumps grow together in a scalelike pattern
that resembles tree lichen. Lichen planus nearly
always occurs in adults.
Symptoms and Diagnostic PathLichen planus typically erupts on the inner sur-
faces of the lower arms and wrists, along the shins
and inner ankles, and along the lower back. Occa-
sionally lichen planus appears on the scalp, where
it can cause temporary or permanent ALOPECIA
(hair loss), or affects the fingernails and toenails,
causing ridges and grooves. In the MOUTH, lichen
planus is light in color and the scaling more dif-
fuse, creating a lacelike pattern lighter in color
than the surrounding mucosa. The distinctive
color and pattern of the RASHallow the dermatolo-
gist to make a quick diagnosis. The doctor may
biopsy lichen planus lesions that appear in the
mouth, as they resemble other conditions (such as
CANDIDIASISand precancerous lesions) that require
different treatment.Treatment Options and Outlook
Outbreaks of lichen planus typically retreat without
medical intervention, thoughANTIHISTAMINE MEDICA-
TIONSand topical CORTICOSTEROID MEDICATIONScan
help relieve the itching. In severe cases, the derma-
tologist may prescribe oral corticosteroids such as
prednisone to suppress the IMMUNE RESPONSE.An
outbreak may last several weeks to several months
and typically flares in irregular recurrences over a
period of years. Gentle, regular skin cleansing and
moisturizing can help to manage and reduce symp-
toms.Risk Factors and Preventive Measures
Dermatologists do not know what causes lichen
planus, though believe it is an immune response
of some sort, either an autoimmune condition or
an immune response to a VIRUS, likely with a
genetic predisposition. Lichen planus also occurs
in HEPATITISC INFECTION, is an early sign of trans-
plant organ rejection, and is a rare SIDE EFFECTof
some medications such as long-term therapy with
the antimalarial medication quinidine and some
NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)
used for OSTEOARTHRITIS. Avoiding exposure to sub-
stances that can cause lichen planus, when identi-
fied, usually prevents future outbreaks though
some people continue to experience cycles of the
condition for several years.
See also AUTOIMMUNE DISORDERS; DERMATITIS;
ICHTHYOSIS; LESION; LEUKOPLAKIA; LICHEN SIMPLEX
CHRONICUS; PRURITUS; PSORIASIS.lichen simplex chronicus A SKIN condition,
sometimes called neurodermatitis, in which an
itchy RASH erupts in response to continued
scratching of the skin. Over time, the involved
areas develop hyperkeratosis, an overgrowth of
keratinocytes that gives the areas a scaly, lichen-lichen simplex chronicus 173