Erythema nodosum

tender erythematous or violaceous nodules usually symmetric on LE Infxn etiol: Strep, TB, EBV, Bartonella, HBV, psittacosis, fungal, L. venereum, etc. Non-infxn etiol: sarcoidosis, IBD, Behçet’s, other rheum, pregnancy/OCP use

• Pursue specific dx based on exposure hx & exam, including serologies, viral PCRs, possibly skin biopsy ± exam of vesicular or bullae fluid if present
• Immunosupp. Pts need broad w/u; higher risk of disseminated/rapidly progressive infxns