Erythema nodosum

Erythema nodosum (EN) is an inflammatory condition characterized by inflammation of subcutaneous fat tissue, resulting in painful red/blue lumps or nodules that are usually seen symmetrically on both shins, on the thighs, arms, and elsewhere. It can be caused by a variety of conditions, but 20 to 50% of cases are idiopathic. It typically resolves spontaneously within 30 days. It is common in young people aged 12–20 years.

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