Erythema nodosum (EN) is a common dermatological eruption characterized by inflammatory nodules of the subcutaneous fat (panniculitis) on the extensor surfaces of the extremities especially the shins, thighs, and forearms. They are usually painful, nodular, bilateral and multiple. They can be found on other areas and be unilateral. They can be red, purple or blackish. They usually resolve without problems in 3-6 weeks.
Diagnosis is usually clinical but biopsy may be needed if there is atypical presentation or history, physical examination or laboratory testing reveals potential underlying diseases. Treatment is usually conservative with rest and non-steroidal anti-inflammatory drugs. Identified underlying causes of the EN should be treated but in some studies more than 50% of t...