Interstitial granulomatous dermatitis in rheumatoid arthritis responsive to etanercept

Interstitial granulomatous dermatitis (IGD) is a rare dermatological condition presenting as erythematous plaques. It may be associated with drug-related adverse reactions and autoimmune diseases. Recent cases of IGD have been reported in rheumatoid arthritis (RA) patients treated with biologic agents. We report a case of RA patient with persistent erythematous plaques who did not respond to traditional disease-modifying anti-rheumatic drugs with a persistent skin condition of erythematous plaque eruptions. A biopsy showed a homogeneous inflammatory infiltrate in the deep dermis composed of large epithelioid histiocytes with occasional granulocytes, leading us to consider a diagnosis of IGD. The cutaneous lesions disappeared after a 3-month treatment with the tumour necrosis factor-α (TNF-α) inhibitor etanercept. Anti-TNF-α agents can antagonise the multiple effects of TNF-α on the immune system, effects that are required for the continued maintenance of granulomatous structure, and offer a therapeutic strategy in the treatment of IGD associated with arthritis.