INTRODUCTION: Interstitial granulomatous dermatitis (IGD) is an uncommon granulomatous dermatitis occurring in the setting of highly reactive immune states, with a polymorphic clinical presentation. Because there is overlap with other entities [namely palisading neutrophilic granulomatous dermatitis (PNGD)], controversy exists regarding its classification. OBJECTIVE: To understand if there are features allowing clear-cut distinction between IGD and PNGD. MATERIAL AND METHODS: Retrospective analysis of 10 cases previously diagnosed as IGD or PNGD, from 2000 to 2013, with review of the histopathologic findings and clinical correlation. RESULTS: Six females and 4 males presented mostly with erythematous papules/nodules (n = 7) but also with erythematous annular plaques (n = 3). In 2 patients, the lesions coexisted. They were mostly distributed symmetrically on the limbs. Associated disease was observed in 6 patients. Regarding histopathology, an inflammatory infiltrate occupying the superficial and mid dermis was present in 40% of cases, with an interstitial component in all biopsies and a palisaded arrangement in 60%. Neutrophils and mononuclear cells were present in all cases in varying proportions. Necrobiosis was found in 70%, and leukocytoclasia was observed in 80% of biopsies. CONCLUSIONS: Coexistence of the interstitial and palisaded inflammatory patterns occurred in 90% of cases, with no correlation between tissue neutrophilia and the predominant pattern of the infiltrate. There was also no clear-cut correlation between the infiltrate pattern and semiologic aspect of the lesions. Therefore, the features described in our study suggest that IGD and PNGD belong to the same clinicopathological spectrum.
INTRODUCTION: Interstitial granulomatous dermatitis (IGD) is an uncommon granulomatous dermatitis occurring in the setting of highly reactive immune states, with a polymorphic clinical presentation. Because there is overlap with other entities [namely palisading neutrophilic granulomatous dermatitis (PNGD)], controversy exists regarding its classification. OBJECTIVE: To understand if there are features allowing clear-cut distinction between IGD and PNGD. MATERIAL AND METHODS: Retrospective analysis of 10 cases previously diagnosed as IGD or PNGD, from 2000 to 2013, with review of the histopathologic findings and clinical correlation. RESULTS: Six females and 4 males presented mostly with erythematous papules/nodules (n = 7) but also with erythematous annular plaques (n = 3). In 2 patients, the lesions coexisted. They were mostly distributed symmetrically on the limbs. Associated disease was observed in 6 patients. Regarding histopathology, an inflammatory infiltrate occupying the superficial and mid dermis was present in 40% of cases, with an interstitial component in all biopsies and a palisaded arrangement in 60%. Neutrophils and mononuclear cells were present in all cases in varying proportions. Necrobiosis was found in 70%, and leukocytoclasia was observed in 80% of biopsies. CONCLUSIONS: Coexistence of the interstitial and palisaded inflammatory patterns occurred in 90% of cases, with no correlation between tissue neutrophilia and the predominant pattern of the infiltrate. There was also no clear-cut correlation between the infiltrate pattern and semiologic aspect of the lesions. Therefore, the features described in our study suggest that IGD and PNGD belong to the same clinicopathological spectrum.