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Plate 4-29 Integumentary System

ERYTHEMA NODOSUM Erythema nodosum
occurs in <5% of
patients with inflam-
Erythema nodosum, an idiopathic form of panniculitis, matory bowel disease.
is seen in association with a wide range of inflammatory The anterior lower legs
and infectious diseases. Pregnancy and use of oral con- is the most frequent
traceptives are two of the most common associations. location.
Erythema nodosum is believed to occur as a secondary
phenomenon in response to the underlying disease
state. The condition typically resolves spontaneously, One of the mainstays of therapy is leg elevation.
but in some cases it is difficult to treat. Erythema
nodosum affects the anterior part of the lower legs
almost exclusively.
Clinical Findings: Erythema nodosum is most com- Main Forms of Panniculitis
monly seen in young adult women. There is no racial
predilection. The skin findings in erythema nodosum Predominantly septal panniculitis
have an insidious onset. Small, tender regions begin Erythema nodosum
within the dermis and develop into firm, tender dermal
nodules, with the anterior lower legs almost always Predominantly lobular panniculitis
involved. The rash typically affects both lower legs in Lipodermatosclerosis
synchronicity. The lesions can be multifocal or solitary in α 1-antitrypsin deficiency
nature. Most patients have multiple areas of involvement, panniculitis
with varying sizes of the lesions. Involvement of other Erythema induratum
areas of the body has been reported but is exceedingly Sclerema neonatorum
uncommon. In these dermal nodules, there is a slight Traumatic panniculitis
red or purplish discoloration to the overlying normal- Pancreatic panniculitis
appearing epidermis. If ulcerations are present, one
should consider another diagnosis, and a biopsy is war-
ranted. Although almost all cases can be diagnosed on
clinical grounds, skin biopsies are required for cases that
are atypical in location or have unusual features such as
ulcerations, surface change, palpable purpura, or other
features inconsistent with classic erythema nodosum.
The diagnosis of erythema nodosum should lead to
a search for a possible underlying association. One of
the most frequent causes is use of oral contraceptive
pills. If the rash is thought to be related to the use of
oral contraceptives, they should be discontinued, after
which the lesions of erythema nodosum typically
resolve. Pregnancy is another major cause of erythema
nodosum. The lesions may be difficult to treat during
pregnancy, but they will spontaneously resolve after
delivery. Erythema nodosum may also be seen in asso-
ciation with sarcoid. Löfgren’s syndrome is the combi-
nation of fever, erythema nodosum, and bilateral hilar
adenopathy that occurs as an acute form of sarcoid. In
patients with no known reason for erythema nodosum,
a standard chest radiograph should be considered to
evaluate for sarcoid or the possibility of an underlying
fungal or atypical infection. Valley fever (coccidioido-
mycosis), which is caused by the fungus Coccidioides
immitis, has been linked with the development of ery-
thema nodosum. Patients presenting with erythema
nodosum who have lived in or traveled to an endemic
area should be evaluated for this fungal infection. Strep-
tococcal infection and tuberculosis are two other infec-
tions that should be considered. Erythema nodosum Erythema nodosum is a panniculitis that predominantly affects the septal portions of the
has also been reported to occur in the inflammatory adipose tissue. The septal tissue is expanded with a lymphocytic infiltrate.
bowel diseases and in Hodgkin’s lymphoma.
Histology: Erythema nodosum is a primary septal
panniculitis. The inflammation is isolated primarily to
the fibrous septa that are present within the subcutane- Pathogenesis: The etiology of erythema nodosum is is withdrawn or after delivery. Those cases associated
ous tissue. The fibrous septa are responsible for provid- unknown, but it is thought to be a hypersensitivity reac- with an underlying infection, malignancy, or inflam-
ing a framework for the adipose tissue. No vasculitis is tion pattern to multiple unique stimuli. It is theorized matory bowel disease may be longer lasting and may
seen, and its presence should make one reconsider the that the antigenic stimulus causes the formation of show a waxing and waning course. Topical corticoste-
diagnosis. The overlying dermis has a superficial and antibody-antigen complexes that localize to the septal roids, compression stockings, elevation, and nonsteroi-
deep perivascular lymphocytic infiltrate. A characteris- region of the adipose tissue. dal antiinflammatory agents are first-line therapies.
tic finding is that of Miescher’s radial granulomas, Treatment: Treatment is primarily symptomatic. Severe cases can be treated with a short course of
which represent multiple histiocytes surrounding a One must pursue the possibility of an underlying dis- prednisone. Supersaturated potassium iodide and
central cleft. Multinucleated giant cells are also present order. Erythema nodosum induced by medications or colchicine have also been reported to be used
within the septal infiltrate. pregnancy resolves spontaneously once the medication successfully.

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