Erythema nodosum

Erythema nodosum is a common form of paniculitis (inflammation of the subcutaneous adipose tissue) with a variety of etiologies, limited to lobular septa and manifested by painful red nodules. Affected are mainly young women (2nd - 4th decade).

Pathogenesis
The mechanism of immunopathological reactions IV. type (delayed type of hypersensitivity) dependent on T-lymphocytes is thought.

Etiology
In about half of the cases, no cause is identified. Of the known causes, the most common are: Furthermore, tuberculosis,  salmonellosis,  idiopathic intestinal inflammation (often a recurrent form).
 * consequence of streptococcal infection (may accompany post-streptococcal arthritis);
 * yersiniosis;
 * sarcoidosis;
 * drugs: hormonal contraceptives, sulfonamides.

Histology
Inflammation, first non-specific, later with the presence of lymphocytes, is limited to the lobular septum of subcutaneous fat. Over time, fibrotization can occur. No vasculitis is present (unlike  polyarteritis nodosa ).

Clinical picture
It quickly forms reddish, painful, a few inches largenodules. The most common location is on the lower legs, less on the extensor sides of the thigh and forearm. Sometimes fever may be present. The lesions may change color as they recede, similar to the hematoma (ie mauve -> yellowish -> greenish) hence the older name erythema contusiforme. The disease resolves spontaneously within a few weeks and leaves no consequences.

Differential diagnosis

 *  erythema induratum Bazin  – paniculitis and vasculitis, most commonly on the calves, caused by TB deposits, can ulcerate
 *  polyarteritis nodosa  – vasculitis
 * other paniculitis and vasculitis

Therapy
We treat the underlying cause, if known. Otherwise, we administer  NSAIDs locally or generally, if it persists for a long time, we use corticosteroids.

Related articles

 * Erythema exsudativum multiforme
 * Paniculitis
 * Sarcoidosis