What are the typical clinical features that distinguish erythema nodosum from other panniculitis conditions

What is known

- Lesions are sudden-onset, symmetrical, bilateral, tender, warm nodules/plaques mainly on the lower limbs, 1–5 cm in diameter. ^1,2 - Ulceration is never seen and nodules heal without atrophy or scarring, resolving within roughly 2–8 weeks. ^1–3 - Nodules show characteristic bruise-like color evolution from bright red to purplish to yellow-greenish. ^1,3 - Histopathology is a predominantly septal panniculitis without vasculitis; Miescher's radial granulomas are a histologic hallmark. ^3,4 - It is often preceded by a prodrome (fever, malaise, arthralgia) and accompanied by systemic symptoms that may point to an underlying cause. ^4–6

What is unknown / caveats

- Excerpts detail EN's own features but give limited direct point-by-point comparison against specific other panniculitides - Diagnosis usually clinical but confirmation requires deep incisional/excisional biopsy including subcutaneous fat - The excerpts characterize EN thoroughly but do not extensively describe the distinguishing features of each competing panniculitis.

## References

1. Requena L, Sánchez Yus E. Erythema nodosum. Semin Cutan Med Surg. 2007. PMID: 17544964.

2. Pekdiker M, Ketenci S. Brucella as an unexpected cause of erythema nodosum. Turk J Phys Med Rehabil. 2022. PMID: 35949956.

3. Requena L, Requena C. Erythema nodosum. Dermatol Online J. 2002. PMID: 12165214.

4. Pérez-Garza DM, Chavez-Alvarez S, Ocampo-Candiani J, Gomez-Flores M. Erythema Nodosum: A Practical Approach and Diagnostic Algorithm. Am J Clin Dermatol. 2021. PMID: 33683567.

5. Blake T, Manahan M, Rodins K. Erythema nodosum - a review of an uncommon panniculitis. Dermatol Online J. 2014. PMID: 24746312.

6. Passarini B, Infusino SD. Erythema nodosum. G Ital Dermatol Venereol. 2013. PMID: 23900162.

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_Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct._