• Notice the infiltration of inflammatory cells between the adipocytes, typical of a lesion of erythema nodosum.

• The lesion represents a common reaction to a variety of of insults to the skin.

•Unknown

•Believed to be a hypersensitvity reaction to varied insults.

•The precise cause of erythema nodosum is unknown, but it can often occur as a sequel to bacterial infections, in response to some drugs and accompanying some fungal infections.

•Common disorder

•It characterisically presents as an exquisitely tender, erythematous lesion.

•Erythema nodosum is usually self-limiting.

•Any underlying associated diseases are treated.

•Erythema nodosum is one form of acute inflammation of the soft tissue of the skin (panniculitis).

•The lesion is often not clearly visible, but can palpated as an area of induration in the subcutaneous tissues.

•Histologically, there are two patterns.

•If the inflammation primarily involves the septa separating the subcutaneous adipose tissue into lobules, there is some thickening of these septa with the presence of inflammatory cells.

•If the inflammation attacks primarily the nodules of fat, areas of fat necrosis with accumulation of inflammatory cells and macrophages is seen.

•Robbins and Cotran: Pathologic Basis of Disease, 7th ed., 2005, p. 1265.

• Current literature from PubMed at National Library of Medicine