Atypical Presentation of Palisaded Neutrophilic Granulomatous Dermatitis

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Dear Editor, Palisaded neutrophilic granulomatous dermatitis (PNGD) is a rare disease with specific clinicopathological characteristics. Herein we present two cases of PNGD with unusual clinical features who got confirmed with histopathology. Case 1 A 60-year-old male with no comorbidities presented with recurrent episodes of crops of multiple well-defined bluish-black, mildly tender, indurated papules, nodules, and plaques over both forearms [Figure 1a] over the last 7 years. No history was suggestive of any auto-immune diseases or other systemic disease. His general and systemic examination was normal. His CRP was 6.5 mg/dL, and his blood sugar was deranged. Rest all serological and biochemical investigations were normal.Figure 1: (a) Involvement of both forearms with multiple bluish-black, mildly tender, indurated papules, nodules, and plaques over both forearms with a peau-de-orange appearance. (b) Two weeks post-therapy showing a reduction in size and erythema of the plaque. (c) Histopathology of case 1 showing dermis with focal areas of collection of neutrophils, histiocytes, and ill-formed granulomas with degenerating collagen fibres (200×) (H and E)Case 2 A 44-year-old female known case of hypothyroidism presented with multiple recurrent painful erythematous papules, nodules, and plaques with ulceration over bilateral buttocks of 3 years duration which resolved spontaneously without any treatment [Figure 2a]. He had a history of pain over multiple joints with early morning stiffness with minimal or no improvement on ayurvedic medication. No history was suggestive of any auto-immune diseases. General and systemic examinations were normal. Her haemoglobin is 9.2 g/dL, total leukocyte count was 14,600/cumm with neutrophilic preponderance, and erythrocyte sedimentation rate was 32 mm/h. C-reactive protein was positive, and the rheumatoid arthritis factor was elevated. The rest of the serological and biochemical investigations were normal.Figure 2: (a) Involvement of both sides of the gluteal region with erythematous plaque and papules. (b) Two weeks of treatment showing a reduction in size and erythema of the plaque. (c) Histopathology of case 2 showing necrobiosis surrounded by palisading granuloma (40×) (H and E)Skin biopsy from the nodules in both patients showed dermis with focal areas of collection of neutrophils, histiocytes along with neutrophilic dust, and ill-formed granulomas with degenerating collagen fibres. Few vessels showed endothelial swelling and scanty cuff of fibrin around the vessel wall [Figures 1b and 2b]. Based on the clinicopathologic correlation, the diagnosis of PNGD was made for which the first patient was started on oral prednisolone along with dapsone 100 mg daily, and the second patient was started on oral steroids along with methotrexate for underlying rheumatoid arthritis. Both patients responded well to treatment in the form of a reduction in pain and size of lesions after 2 weeks of therapy and are on follow-up with no recurrence in the last 6 months [Figures 1c and 2c]. PNGD is commonly associated with rheumatoid arthritis, autoimmune connective tissue diseases, lymphoproliferative disorders, sarcoidosis, vasculitis, infection, and inflammatory bowel disease.[1] Several names of PNGD include rheumatoid papules, linear subcutaneous bands, interstitial granulomatous dermatitis with cutaneous cords and arthritis, superficial ulcerative rheumatoid necrobiosis, and Churg-Strauss granuloma.[2,3] Etiopathogenesis of PNGD includes abnormal neutrophil activation, circulating immune complex deposition, a delayed-type hypersensitivity reaction, low-grade small vessel vasculitis, or drug-associated.[4] Even though its clinical presentation varies, PNGD usually presents as skin-coloured to erythematous papules or plaques with central umbilication or necrosis mostly distributed symmetrically on the extensor surfaces of the upper extremities, head, or neck. Although most people are asymptomatic, they may experience pain, soreness, or itching.[5] The clinical differential diagnosis includes leukocytoclastic vasculitis, urticaria, interstitial granulomatous dermatitis, and granuloma annulare. The pathologic characteristics enable the diseases to be differentiated. Early lesions show a dense neutrophilic infiltration with or without cutaneous small-vessel vasculitis and collagen degeneration. Fully developed lesions show palisaded granulomas surrounding degraded collagen, with interstitial fibrin and mucin deposits, few neutrophils, and nuclear dust. Furthermore, the clearing lesions reveal palisaded granulomas with dermal fibrosis and infrequent neutrophilic debris.[6] PNGD may persist for months to years before resolving on its own, and treatment includes steroids, colchicine, cyclosporine, cyclophosphamide, and dapsone. We report these unusual signs of PNGD to raise awareness among dermatologists and the importance of histopathology in diagnosis. Consent Written and verbal informed consent for usage of images in publication have been properly obtained from the patients. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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