Interstitial granulomatous dermatitis: a characteristic histological pattern with variable clinical manifestations

Interstitial granulomatous dermatitis (IGD) is a distinct histopathological pattern with a diverse clinical appearance which can be associated with autoimmune systemic diseases or, rarely, with drug-related adverse reactions. The IGD is a rare entity, first described in 1993 by Ackerman, which belongs to a group of non-infectious cutaneous granulomas [1]. The disease affects mostly women, at the mean age of onset at 58 years [2]. The precise etiopathogenesis remains unknown, but the underlying inflammatory process of the dermis and granulomatous infiltrate can be involved in the development of the disease. One hypothesis suggests that the depositions of immune complexes in the dermal vessels may be the trigger, which is then followed by complement and neutrophil activation and damage of dermal collagen, which in response gives rise to a granulomatous infiltrate [3]. We present a case of IGD that seems to be a distinct entity with variable clinical manifestations, which can be easily differentiated from other granulomatous skin diseases on the basis of histopathological examination. Although the disease occurs more frequently in adults, we present a case of IGD in a child.
An 8-year-old girl was admitted for the evaluation of skin lesions of more than 2-year duration. She was initially clinically diagnosed as granuloma annulare and treated empirically with potent topical glucocorticoids without any clinical improvement. Physical examination revealed indurated, sharply demarcated, slightly erythematous, painless plaques on her right shank and single nodules on the thighs (Figure 1). She denied any systemic complaints. Family history of similar lesions and autoimmune disorders was unremarkable. No significant precipitating factors preceded skin lesions. A complete blood count, metabolic panel, C-reactive protein and rheumatoid factor were within the normal range. The titer of antinuclear antibodies was 1 : 1280. Anti-Ro, anti-La, anti-RNP and anti-Smith antibodies were negative. The histopathological examination of skin biopsy from the lesion on the right shank revealed band-like infiltrate of histiocytes in the reticular dermis with focal areas of bundles palisading around necrotic collagen (Figure 2). Based on the overall clinicopathological findings, we diagnosed interstitial granulomatous dermatitis. Due to poor results of treatment with topical corticosteroids, therapy with dapsone was implemented at a dose of 25 mg per day (the body weight – 25...


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