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Skin-nontumor / Clinical Dermatology

Other dermatoses

Erythema nodosum

Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns (Canada (see Reviewers page)
Revised: 25 July 2011, last major update July 2011
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.


● Panniculitis with tender red nodules, usually on both shins

Clinical features

● Red, painful, bilateral, symmetrical nodules, elevated above the skin surface
● On anterior surface of legs, arms, face, calves and trunk
● Usually involutes in days/weeks, leaving depressed, pigmented lesions
● No ulceration
● Immune mediated, but precise mechanism is unknown
● May be associated with streptococcus infection, tuberculosis, sarcoidosis, coccidioidomycosis, ulcerative colitis, Behcet’s disease, drug reactions or idiopathic; also Hodgkin lymphoma, renal cell carcinoma and carcinomas of colon, pancreas and uterine cervix


● Erythema nodosum migrans (subacute nodular migratory panniculitis, migratory panniculitis): asymmetrical, unilateral, and distributed solely on the legs; marked female predominance; older age group
● Chronic erythema nodosum: nodules appear over months/years; otherwise indistinguishable from typical condition

Clinical images

Erythematous nodules and plaques on anterior legs; patient had also ulcerative colitis

Early erythema nodosum in young woman taking birth control pills

Micro descriptions

● A prototype of septal panniculitis, characterized by vascular changes, septal inflammation, hemorrhage and variable acute and chronic panniculitis
● Both septal and lobular panniculitis
● Marked septal fibrosis, infiltrated by lymphocytes, neutrophils, histiocytes and granulomas with giant cells
● Septal infiltrate spills over to affect the fat lobules
● Dermis shows perivascular and periadnexal chronic inflammatory cell infiltrate
● Early, the septal inflammation is acute and characterized by neutrophils, soon replaced by lymphocytes and histiocytes
● Variable eosinophils, variable vasculitis
Miescher’s radial granuloma: characteristic finding of erythema nodosum; septal collection of histiocytes surrounding a cleft (appear to look like spaces); reported in Sweet’s syndrome, nodular vasculitis and necrobiotic lipodica

Micro images

Perivascular infiltrate

Inflammatory infiltrate extending along fibrous septa of adipose tissue

Septal panniculitis and Miescher's granulomata

Differential Diagnosis

Nodular vasculitis or subacute nodular migratory panniculitis: usually septal
Weber-Christian disease associated panniculitis: usually lobular inflammation

Additional references

More information

End of Skin-nontumor / Clinical Dermatology > Other dermatoses > Erythema nodosum

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