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 erythematous 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-positive macrophage infiltrate distributed between collagen bundles of the mid- and deep dermis. Macrophages were also surrounding degenerated collagen fibres. A few neutrophils and/or eosinophils were also present. No vasculitis or significant mucin deposition was observed. Of the 62 cases of IGD reported since 1993, 53 fulfilled stringent diagnostic criteria. Erythematous papules and plaques on the trunk and proximal limbs were the dominant manifestation. Approximately 10% 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 be clarified. Patients should be screened for rheumatic and autoimmune diseases.