Telling erythema nodosum from other panniculitis

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.