Page 135 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-50 Rashes

NECROBIOSIS LIPOIDICA

Necrobiosis lipoidica is a rash that is frequently encoun-
tered in the dermatology clinic. It is most commonly
seen in association with diabetes and is referred to as
necrobiosis lipoidica diabeticorum. However, not all
cases are seen in conjunction with diabetes mellitus, and
the name necrobiosis lipoidica is a more inclusive designa-
tion. Patients who present with necrobiosis lipoidica
should all be evaluated for underlying diabetes and
screened periodically over their lifetime, because 60%
to 80% will have or develop some form of glucose
intolerance. Necrobiosis lipoidica has been reported to
appear any place on the skin, but it is most frequently
encountered on the anterior lower extremities. It has a
characteristic clinical appearance, and the diagnosis can Medium power. A mixed granulomatous infiltrate is
often be made on clinical grounds alone, without the present throughout the dermis, and there is a “cake
use of a skin biopsy. The histologic findings are diag- layering” effect.
nostic of necrobiosis lipoidica. A punch or excisional
biopsy is required for diagnosis, because a shave biopsy
does not allow for proper histological evaluation of this
condition.
Clinical Findings: There appears to be no sexual or
racial predilection, and the disease is most commonly
diagnosed in early adulthood. In most instances, necro-
biosis lipoidica occurs on the anterior lower extremities.
The rash typically begins as a tiny red papule that
slowly expands outward and leaves behind a depressed,
atrophic center with a slightly elevated rim. The
borders are very distinct. They are slightly elevated
and have a more inflammatory red appearance. They
are well demarcated from the surrounding normal-
appearing skin. The lesions have a broad range of sizes,
from a few millimeters in some cases to affecting the
entire aspect of the anterior lower legs. The plaques
have a characteristic orange-brown coloration and sig- High power. Close-up view of a layer of necrobiotic
nificant atrophy. The underlying dermis appears to be collagen between two layers of diffuse granulomatous
thinned dramatically; the dermal and subcutaneous inflammation
veins can easily be seen and appear to be popping out
of the skin. When palpated, the center of the lesions
feel as if there is no dermal tissue present at all. The
difference between palpation of the normal skin and
palpation of affected skin is striking.
A small percentage of patients experience ulcerations
that can be slow and difficult to heal. Rarely, transfor- Atrophic patch on the anterior lower leg. Dermal blood vessels
mation of chronic ulcerative necrobiosis lipoidica into are prominently seen. This rash can be associated with diabetes.
squamous cell carcinoma has been reported. This trans-
formation is more likely to be a result of the chronic
ulceration and inflammation than the underlying nec-
robiosis lipoidica. There are no other associations with
necrobiosis lipoidica except for diabetes.
Pathogenesis: The pathomechanism of necrobiosis
lipoidica is unknown. Theories have been suggested, but
no good scientific evidence has pinpointed the cause.
Histology: The histology of necrobiosis lipoidica is
characteristic. A punch or excisional biopsy is needed
to ensure a full-thickness specimen. There is a “cake
layering” appearance to the dermis, with necrobiotic
collagen bundles within palisaded granulomas alternat-
ing with areas of histiocytes and multinucleated giant
cells of both the foreign body and the Langhans type.
The differential diagnosis histologically is between corticosteroid creams, which can cause atrophy. In cases placebo-controlled studies. Gaining control of the
granuloma annulare and necrobiosis lipoidica. In nec- of necrobiosis lipoidica, however, the high-potency underlying diabetes does not seem to play a role in the
robiosis lipoidica, the inflammatory infiltrate contains steroid agents do not lead to an increase in the atrophy. outcome of the skin disease. Ulcerations should be
less mucin and more plasma cells. The inflammation in The steroid agents act to decrease and stop the inflam- treated with aggressive wound care, and compression
necrobiosis lipoidica also tends to extend into the sub- matory infiltrate from occurring and perpetuating garments should be worn if edema or venous insuffi-
cutaneous adipose tissue. itself. Intralesional injections of triamcinolone have also ciency is present. Ulcers may take months to heal. Once
Treatment: Treatment is typically initiated with the been successful. Many other agents have been anecdot- the inflammation has been stopped, most people have
use of high-potency topical steroids. It may seem coun- ally reported to be successful in treating this condition, residual atrophy that may be permanent or may improve
terintuitive to treat an atrophic condition with topical although they have not been tried in standardized, slightly with time.

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