Interstitial Granulomatous Dermatitis Associated With Chronic Inflammatory Demyelinating Polyneuropathy

A 44-year-old man presented with an eruption of pruritic erythematous plaques on his lower extremities of 6 months’ duration that were unresponsive to antifungal cream or topical corticosteroid. His medical history was notable for chronic inflammatory demyelinating polyneuropathy (CIDP), which was diagnosed 1 year prior to presentation and was associated with lower extremity weakness and imbalance of 3 years’ duration. Punch biopsy of lesional skin showed a superficial and deep perivascular and interstitial lymphohistiocytic infiltrate with abundant interstitial neutrophils and rare eosinophils. He was diagnosed with interstitial granulomatous dermatitis (IGD), and the eruption improved with the initiation of oral dapsone 50 mg twice daily.