Erythema Nodosum

Diagnosis: Erythema Nodosum

Slightly elevated, dusky erythematous nodules that have become confluent on edematous legs.

Clinical Presentation

Slightly elevated, dusky erythematous nodules that have become confluent on edematous legs.

Clinical History

Submitted by Alaa Saad. Originally posted September 21, 2010.

Treatment

See case discussion.

Differential Diagnosis

• Panniculitis (other forms) • Cellulitis • Superficial thrombophlebitis • Polyarteritis nodosa • Sweet syndrome • Vasculitis • Insect bite reactions • Sarcoidosis (subcutaneous)

Key Learnings

• Most common form of panniculitis — septal panniculitis without vasculitis • Bilateral, pretibial, tender, erythematous nodules • Etiology: infections (Streptococcus #1), sarcoidosis, IBD, drugs (OCPs, sulfonamides), pregnancy, idiopathic (~50%) • Biopsy shows septal panniculitis with Miescher's radial granulomas — pathognomonic • Self-limited, resolves in 3-6 weeks without scarring or ulceration • Lesions evolve through bruise-like color changes (erythema → violaceous → yellow-green) • No biopsy needed if classic presentation — biopsy for atypical or persistent cases

Tags: erythema, nodosum, alaa saad