pathology
Last reviewed 03/2021
Erythema nodosum represents an inflammation of the septa in the subcutaneous adipose tissue (a septal paniculitis) (1)
Evidence suggests that erythema nodosum develops as a type IV delayed hypersensitivity response to a number of antigens e.g - streptococcal infection, tuberculosis, fungal infection, leprosy and some drugs (1,2).
The histopathology is distinctive:
- early lesions show widening of the connective tissue between lobules and may be associated with hemorrhage (1)
- a characteristic finding of the disease is Actinic (Miescher's) radial granulomas – these are well demarcated, small, nodular collections of tiny histiocytes around a central stellate cleft (1)
- later there is an cellular infiltrate containing lymphocytes, histiocytes and multinucleate giant cells
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