Interstitial granulomatous dermatitis with arthritis

Background: Interstitial granulomatous dermatitis with arthritis is an uncommon systemic disorder involving the cutaneous and musculoskeletal systems. The eruption may mimic other dermatoses including granuloma annulare, erythema chronicum migrans, and the inflammatory stage of morphea. Key histopathologic characteristics, along with clinical correlation, allow accurate diagnosis. Objective: We describe the clinical, serologic, and histologic features in three patients with interstitial granulomatous dermatitis with arthritis. Methods: Skin biopsy specimens were examined and correlated with the clinical and laboratory findings. Results: Erythematous, annular, indurated plaques on the extremities were present in two women. An erythematous, papular eruption on the head and neck was present in a third patient. All patients had myalgia and migratory polyarthralgias of the extremities along with various serologic abnormalities. Histologic examination revealed a dense lymphohistiocytic interstitial infiltrate involving primarily the reticular dermis. Foci of necrobiotic collagen were present. Vasculitis was absent. Conclusion: Interstitial granulomatous dermatitis with arthritis is a unique multisystem disease with variable cutaneous expression. Abnormal serologic findings indicate a possible connection to collagen vascular disease.