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

Background Interstitial granulomatous dermatitis(IGD) is a rare disease for which a clinical pathological correlation is essential to establish diagnosis. Objectives To describe the histological and clinical features of patients with IGD seen in our department from 2004 to 2010, and to undertake a literature review and critical analysis of additional cases. Methods Twelve adult patients (nine women and three men; mean age 58.5 years; range 32-73 years) with IGD were enrolled. Lesions consisted of asymptomatic cry thematous papules and plaques, symmetrically distributed on the trunk and the proximal limbs. Two patients had skin coloured papules. Six patients had articular involvement (arthralgias, spondyloarthritis, rheumatoid arthritis) and three patients had cancer. Results All cases showed a predominant CD68 jtositl Sc itiacropl age infiltrate dis tributed between collagen bundles of the mid- and deep dermis. Macrophages were also surrounding degenerated collagen fibres. A few neutrophils and/or eo sinophils were also present. No vasculitis or significant mucin deposition was observed. Of the 62 cases of IGD reported since 1993, 53 fulfilled stringent dhag nostic criteria. Dry thematous papules and plaques on the trunk and proximal Ii mbs were the dominant manifestation. Approximately 100,/o of patients had cord like lesions. More than 50% of patients with IGD had arthralgia or arthritis, and less commonly other rheumatic disorders. Disease duration is months to years, but long term prognosis seems favourable. Conclusions 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 he clarified. Patients should be screened for rheumatic and autoim mune diseases.