Interstitial granulomatous dermatitis: a distinct entity with characteristic histological and clinical pattern

Abstract

IGD is a distinct entity with a typical histological and clinical pattern. The importance and the nature of the association with extracutaneous diseases remains to be clarified. Patients should be screened for rheumatic and autoimmune diseases.

Reactive Granulomatous Dermatitis

“…42 Similar to PNGD, there is a 3:1 female to male predominance, 38 again likely owing to the association with underlying autoimmune diseases. The initial description of IGD was that of linear subcutaneous cords or bands on the proximal trunk, 32 although over time the clinical morphologic spectrum has expanded and many feel that other presentations are in fact more common with cords reported in less than 10% of cases.…”

“…3). 38 Other clinical morphologies reported include small skin colored papules, 38 50 periungual and mucosal erythema, 51 and even elbow papules and nodules similar to those of PNGD. 52 The skin lesions are generally symmetric on the lateral upper trunk and proximal inner arms and proximal thighs (although reports exist of lesions on the buttocks, abdomen, breast, and umbilicus 53 ), and are usually asymptomatic.…”

“…The inflammatory infiltrate is composed of CD68 1 epithelioid histiocytes in the majority of cases. 38 The histiocytes may form small granulomas, and often clusters of histiocytes can rim abnormal collagen and lead to visible clefting, which has been termed the "floating sign," reported in two-thirds of cases. 38 Although rare, eosinophils and neutrophils may be seen, 54 and vasculitis is generally absent in IGD (1 case reported vasculitis, albeit with no histologic image, 36 with more than 35 other reports lacking vasculitis).…”

“…The initial description of IGD was that of linear subcutaneous cords or bands on the proximal trunk, 32 although over time the clinical morphologic spectrum has expanded and many feel that other presentations are in fact more common with cords reported in less than 10% of cases. 38 Beyond the ropelike, linear cord lesions, 32,43 erythematous to violaceous patches or plaques symmetrically on the upper trunk and proximal limbs are a frequent manifestation (Fig. 3).…”

“…The histologic findings include variably dense interstitial histiocytes often surrounding foci of abnormal collagen leading to "clefting" away of the altered collagen and histiocyte section, termed the "floating sign." 38 As with PNGD, the clinical (and to a lesser extent the histologic) spectrum of IGD has expanded, and coupled with the complex, evolving nomenclature and confusion over whether IGD represents a distinct entity or a subset of PNGD, has proven a source of confusion to both clinicians and readers of the scientific literature.…”