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Pathology of Erythema Nodosum

Dr Sampurna Roy MD       


Path Quiz Case 86: Case history and images

Diagnosis: Erythema Nodosum




Erythema nodosum is a disease characterized by painful , erythematous nodular lesions.

It is the most common panniculitis and histologically represents the prototype of a septal panniculitis.


Situated on the anterior and lateral aspect of the lower extremities and rarely on the arms, trunk, and calves, and on the neck and face.


Usually occurs in young adults. Cases have been reported in children and in elderly patients.


It is not known and may be due to allergic response to infection or systemic disease.

Erythema nodosum is associated with the following conditions:

- Infection : Streptococcal ;Meningococccal ;Campylobacter ; Salmonella ; Histoplasma ; Mycobacterial ; Dermatophyte ; Yernia.

- Sarcoidosis (2nd most common cause)

- Inflammatory bowel disease ; Behcet disease ; Sweet's disease ; Carcinoma ; lymphoma ; leukemia.

Other triggering factors include drugs (Example: Sulphonamides ; penicillin ; oral contraceptive) and radiotherapy.

Microscopic features:   

Septal panniculitis:

Small foci of inflammatory cells extend into adjacent lobular fat ; 

Sometimes spillover of cells is prominent and include foam cells ;

There may be focal fat necrosis adjacent to the septa;

Septal infiltrate is composed of lymphoid cells, variable numbers of foreign body giant cells and occasional eosinophils and histiocytes ;

In fully developed lesions granulomas are present in the center of lobules ;

A  clue helpful to diagnosis of an early lesion of erythema nodosum is the finding of "radial" granulomas, first described by Miescher and consisting of clusters of neutrophils in collections of epithelioid histiocytes ;

A few neutrophils  are present in the early lesion ;

Fibrous septa in the subcutaneous fat are widened by edema ;

Mild to moderate perivascular infiltrate of lymphocytes around vascular plexuses of the reticular dermis ;

Sometimes a definite vasculitis is present (lymphocytic or leukocytoclastic type).

In late lesions septa widened by marked fibrosis ;  

Fat lobules are  markedly reduced in size by widened fibrotic septa.


Further reading:

Erythema nodosum.

The role of skin biopsy in diagnosis of panniculitides.

Erythema nodosum-like lesions in Behçet's disease: a clinicopathological study of 26 cases.

Combined reduced-antigen content tetanus, diphtheria, and acellular pertussis (tdap) vaccine-related erythema nodosum: case report and review of vaccine-associated erythema nodosum.

Histopathologic spectrum of erythema nodosum.

Erythema nodosum.

Panniculitis. Part I. Mostly septal panniculitis.

Histopathologic features of erythema nodosum--like lesions in Behcet disease: a comparison with erythema nodosum focusing on the role of vasculitis.

Erythema nodosum versus nodular vasculitis.

Miescher's radial granuloma. A characteristic marker of erythema nodosum. 




Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

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