tinea versicolor is not contagious. The FUNGUS
responsible, Malassezia furfur, is normally present
on the skin (NORMAL FLORA). Dermatologists do not
know why the fungus causes infection in some
people and not in others, though they suspect the
infection is opportunistic in being able to gain a
foothold when other challenges are occupying the
IMMUNE SYSTEM. Treatment is typically a combina-
tion of topical and oral ANTIFUNGAL MEDICATIONS. As
M. furfuris normal flora, tinea versicolor tends to
recur in people who are susceptible to it. When
recurrences are frequent, the dermatologist may
prescribe prophylactic antifungal therapy.
See alsoVITILIGO.
tissue expansion A method for growing addi-
tional SKINto use for autologous (self) skin grafts.
Autologous grafts have the best rate of success
when transplanted because they are native to the
body and present no risk for graft rejection. Tissue
expansion is a common method for many recon-
structive surgery procedures, though requires ade-
quate areas of healthy skin.
For tissue expansion, the surgeon makes a
small incision to create a pouch or pocket in
healthy skin and inserts a balloonlike pouch called
a tissue expander. The surgeon then adds a small
amount of saline, through a special valve, every
few days or so over a period of several months.
The expander encourages the skin to grow to
cover it, slightly accelerating the rate of growth
over that which would normally occur. When the
new growth of skin reaches the desired surface
area, the surgeon removes the expander and can
harvest the skin to transplant elsewhere on the
body. Tissue expansion grafts are highly successful
for repairing skin surfaces damaged or lost to
severe BURNSor injuries. Some HAIR TRANSPLANTA-
TIONmethods also use tissue expansion to grow
additional skin that contains healthy hair follicles.
As with any surgery, the primary risks associ-
ated with tissue expansion are INFECTION and
excessive bleeding. The tissue expander generally
creates a conspicuous bulge in the surface of the
skin, though the skin profile at the growth site
returns to normal when the surgeon removes the
expander. The surgeon uses appropriate tech-
niques to minimize scarring at the harvesting site
as well as during placement of the new skin.
See also PLASTIC SURGERY.toxic epidermal necrolysis A life-threatening
inflammatory condition affecting the SKIN and
underlying connective tissues, also called Stevens-
Johnson syndrome. Toxic epidermal necrolysis
usually results as an adverse DRUGreaction though
may occur as a complication of INFECTION or
CANCER. Doctors believe toxic epidermal necrolysis
develops when an external event triggers the
mechanism for programmed cell death (apopto-
sis), causing massive numbers of keratinocytes
(the cells that primarily comprise the skin) to die.
This in turn activates the body’s IMMUNE RESPONSE,
which attacks the dying cells. The massive death
of keratinocytes results in large segments of skin
sloughing off, leaving the underlying tissue
exposed. Toxic epidermal necrolysis typically
evolves over a period of 10 to 14 days, though
once the skin eruptions begin deterioration is
rapid.
Diagnosis is by skin biopsy, which shows the
characteristic pattern of cell destruction and abun-
dance of killer T-cells. In most situations the first
line of treatment is plasmapheresis, a process
somewhat similar to dialysis in which a mechani-
cal BLOOD separator removes the serum and
replaces it with donor serum. Plasmapheresis
helps clear antibodies from the serum, reducing
the immune response. Other treatments include
frequent surgical débridement of skin surfaces,
skin grafts to cover denuded surfaces, and precise
fluid and electrolyte replacement.
Toxic epidermal necrolysis has a survival rate
of about 60 percent. Those who survive often
have long-term complications and face a challeng-
ing road to rehabilitation and recovery. The mas-
sive loss of skin causes extensive scarring similar
to that of serious BURNS. The eyes also experience
damage as the sloughing affects the conjunctiva
and sclera (EYEtissues).
See also ADVERSE REACTION; ANTIBODY; HEMAPHERE-
SIS; KERATINOCYTE; STAPHYLOCOCCAL SCALDED SKIN SYN-
DROME.urticaria The clinical term for hives, an outbreak
of wheals on the SKIN’s surface. Acute urticaria,
which comes on suddenly, typically signals a
HYPERSENSITIVITY REACTION. The wheals contain fluidurticaria 205