Page 129 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-44 Rashes

LICHEN SIMPLEX CHRONICUS

Lichen simplex chronicus is a commonly encountered Lichenified plaques
chronic dermatosis that can be initiated by many events. on the ankles. Note
Certain regions of the body are more prone to develop the accentuation
lichen simplex chronicus, such as the lower leg and of the skin lines
ankle region and the posterior scalp, but it can occur with a significant
anywhere. The initiating factor can be any skin insult thickening
that induces itching. The itch-scratch cycle is never of the skin.
broken, and the skin in the region being manipulated
takes on a lichenified appearance. This is believed to be
a localized skin condition that has no systemic associa-
tions or causes. Many therapies have been attempted
with varying rates of success.
Clinical Findings: There is a slight female prepon-
derance and no racial predilection. Most patients who
present with lichen simplex chronicus do not relate an
underlying insult that initiated the chronic itching.
Some report a previous bug bite, trauma, or initiating
rash such as allergic contact dermatitis caused by poison
ivy. Involvement is localized to one region of the body,
most often the ankle. Other commonly involved areas
are the occipital scalp and the anogenital region.
Patients report that they have a constant itching or
burning sensation, and they respond to it by chronically
rubbing or itching the area. Initially, a fine red patch
with some excoriations is present. As the condition Lichen simplex chronicus is common in the genital
becomes chronic, the rash takes on the clinical appear- region of both males and females. It manifests with
ance of lichen simplex chronicus. The skin becomes relentless pruritus and lichenification of the affected skin.
thickened and lichenified. There is an accentuation of
the normal skin lines, and the region of involvement
shows varying degrees of hyperpigmentation. Small
excoriations and even small ulcerations may occur if
the pruritus is severe and the patient cannot control
the itching.
The cycle of pruritus and itching is perpetuated and
can last for years to decades if untreated. Patients often
relate that stressful events can initiate a flare of pre-
existing lichen simplex chronicus. They also commonly
state that the itching is worse during the evening hours
just before sleep. The main theory to explain this is that
the cortex is not as busy processing information at that
time, and other areas of the brain that are responsible
for itching become activated or become disinhibited
from cortical control. Even with treatment, some cases
last for years. Patients typically become frustrated with
therapy and are willing to pursue the help of other
physicians or ancillary medical caregivers, such as acu-
puncturists. A fully developed area of lichen simplex
chronicus is a well-defined lichenified plaque with exco-
riations and blood-tinged crust.
Pathogenesis: The exact pathomechanism of devel-
opment of lichen simplex chronicus is unknown. Initiat-
ing events have been investigated, including insect bite
reactions, underlying atopic diathesis, anxiety, stressful Acanthosis with elongation of the rete ridges. Patchy hyperkeratosis and
events, and other psychiatric conditions. Many patients parakeratosis. Vertically arranged collagen is present within the dermal papilla.
have none of these factors, yet the clinical and patho-
logical picture is identical.
Histology: The epidermis is acanthotic with elonga-
tion of the rete ridges. A varying amount of parakera- Treatment: Therapy is often directed at breaking the used. This agent works by depleting the superficial
tosis is present, with excoriations and superficial itch-scratch cycle. This is attempted with a combina- nerve endings of substance P, the neurotransmitter
ulcerations observed in some cases. The collagen tion of topical high-potency corticosteroids and oral required for the itching sensation. Patients should be
bundles within the papillary dermis show a vertical antihistamines or gabapentin. The sedating antihista- advised to trim their fingernails to help prevent trauma
arrangement, parallel to the rete ridges. The rete ridges mines work better than the newer, nonsedating ones. when they scratch. Behavioral modification may be
are irregular in elongation, unlike the regular pattern Topical steroids may be used under occlusion for better attempted, but it is best accomplished by a professional
seen in psoriasis. A varying degree of epidermal spon- penetration of the lichenified region. Intralesional psychiatrist or psychologist. Precipitating causes such
giosis is seen, but no epidermotropism. The inflamma- injection with triamcinolone may be attempted. Capsa- as stress should be addressed. Patients often have remis-
tory infiltrate is composed primarily of lymphocytes. icin, which is derived from capsicum peppers, may be sions with frequent relapses.

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