Track

Clinical Studies

Abstract

Reactive granulomatous dermatitis (RGD) is a recently proposed unifying term for interstitial granulomatous dermatitis, palisaded neutrophilic and granulomatous dermatitis, and interstitial granulomatous drug reaction. Few large studies exist characterizing this rare entity. In this retrospective study, we described the spectrum of clinical and histopathologic manifestations and comorbidities in a relatively large cohort of patients with RGD. Patients were selected by searching the Patient Data Registry for the keywords “interstitial granulomatous dermatitis” in pathology reports between 1/1/2000 and 10/31/2022. 227 charts were screened; clinical information was available for 65 patients. Majority were female (70.8%) and white (90.8%). Median age was 60. Cutaneous lesions most frequently occurred in the upper (60%) and lower extremities (43.1%). Erythematous to violaceous patches and plaques were seen in 49.2% of patients. Most lesions were asymptomatic (44.6%); pruritus was the most frequent symptom (26.1%). Lymphohistiocytic cell infiltration was seen in 76.9% of biopsies. Accompanying cells were eosinophils (26.1%), neutrophils (13.8%) and plasma cells (1.54%). A palisading pattern was observed in 23.1%. Alcian blue staining demonstrated mucin in 38.5% of biopsies. Vascularity was seen in 3.08%, necrobiosis in 18.5%, and fibrinoid necrosis in 4.61%. Leukocytoclastic vasculitis was determined in 4.61%. Autoimmune/inflammatory comorbidities were observed in 73.8% of patients, most commonly hypothyroidism (24.6%), Raynaud’s disease (10.8%), and psoriasis (9.23%). Malignancies were observed in 33.8%, most frequently hematologic malignancy (15.4%), melanoma (7.69%), and breast cancer (7.69%). In conclusion, RGD presented with a broad range of clinical and histopathologic features, and high frequency of autoimmune/inflammatory and malignancy comorbidities in this patient cohort.