Rheumatoid neutrophilic dermatitis (RND) is a rare cutaneous disorder closely associated with rheumatoid arthritis (RA), belonging to the category of neutrophilic dermatoses [1] . The condition was first described in 1978 and is predominantly observed in seropositive RA patients, though rare cases have also been reported in seronegative individuals [2] . Clinically, RND typically presents as symmetrical erythematous papules, nodules, and plaques on extensor surfaces, whereas annular vesicles, pustules, or ulcerations are uncommon; lesions mainly affect the extremities [3] . Histopathologically, RND is characterized by dense neutrophilic infiltrates in the dermis without vasculitis. Direct immunofluorescence (DIF) is typically negative. The exact pathogenesis of RND remains unclear, though it is believed to represent a cutaneous manifestation of RA-associated systemic immune dysregulation, possibly involving immune complex deposition and abnormal cytokine activity, particularly IL-6 and IL-8 [4] . RND should be differentiated from other neutrophilic dermatoses. The condition may resolve spontaneously or improve with RA treatment. Therapeutic strategies include topical or systemic corticosteroids, colchicine, dapsone, hydroxychloroquine, and biologic agents [5] . Given its rarity, we report a rare case of RND with annular vesicles managed at our institution.

Rheumatoid neutrophilic dermatitis (RND) is a rare neutrophilic dermatosis that represents a cutaneous manifestation of severe rheumatoid arthritis (RA) [6] . It falls within the spectrum of neutrophilic dermatoses and predominantly affects middle-aged females. RND is closely associated with RA disease activity and systemic inflammation, typically occurring during active RA phases or in patients presenting with systemic symptoms. Serologic markers such as rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies are often strongly positive [2] . RND typically presents with symmetrical skin lesions affecting the extensor surfaces of the extremities, trunk, and buttocks. The lesions may appear as erythematous or violaceous papules, plaques, nodules, urticarial lesions, or ulcers. Bullae, pustules, annular lesions, petechiae, and purpura may also be observed. The condition is generally asymptomatic, though some patients experience mild pruritus or pain [7] . Associated symptoms, including joint swelling, morning stiffness, and restricted mobility, are reflective of underlying RA activity.

The exact pathogenesis of RND remains incompletely understood, but it is believed to involve multiple mechanisms. First, RND predominantly occurs in patients with active or severe RA, a systemic autoimmune disease characterized by chronic inflammation and tissue damage [8] . This inflammatory milieu may directly or indirectly contribute to cutaneous involvement. Second, a hallmark of RND is the presence of dense dermal neutrophilic infiltrates without vasculitis, suggesting that excessive neutrophil recruitment, activation, and chemotaxis play a key role in disease pathogenesis. Third, RA is associated with immune complex formation and deposition, which may trigger localized inflammatory responses. In RND, immune complexes may accumulate within the dermis, leading to neutrophil recruitment and activation. Finally, the inflammatory environment in RA is rich in cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8), which can enhance neutrophil activity and stimulate cutaneous cells to release additional inflammatory mediators, contributing to RND pathogenesis [1] . Although the pathophysiology of RND is complex, it is ultimately considered a specific cutaneous manifestation of the systemic immune dysregulation seen in RA.

Due to the rarity of RND, standardized diagnostic guidelines are lacking, and diagnosis is based on a combination of clinical, laboratory, and histopathological findings. RND should be suspected in patients with seropositive RA who develop characteristic cutaneous lesions during active disease phases. Laboratory findings often show elevated RF and anti-CCP antibody titers. Inflammatory markers such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) may be elevated, reflecting active systemic inflammation. Peripheral blood neutrophilia may also be present. The gold standard for diagnosis is histopathology, which reveals dense neutrophilic infiltration in the dermis without evidence of leukocytoclastic vasculitis. DIF is typically negative, which helps differentiate RND from immune complex-mediated vasculitides and autoimmune blistering diseases.

Additionally, conditions such as pyoderma gangrenosum (PG), Sweet syndrome, Behcet’s disease, and erythema elevatum diutinum (EED) must be ruled out [9] . RND lacks pathognomonic cutaneous or histological features, necessitating differentiation from other neutrophilic dermatoses. EED is characterized by symmetrically distributed violaceous plaques and nodules on extensor surfaces, with histopathology showing lymphocytic infiltration and leukocytoclastic vasculitis [10] . The absence of vasculitis in this case excludes EED. PG begins with inflammatory papules, pustules, or nodules that rapidly progress to painful ulcers, primarily on the lower extremities [11] . Histopathology reveals dermal neutrophilic infiltrates, abscess formation, vasculitis, and necrosis, with DIF showing local immune complex deposition. The absence of ulcerative lesions and vasculitis in this patient excludes pyoderma gangrenosum. Sweet syndrome presents as painful erythematous plaques or nodules, often with systemic symptoms such as fever and arthralgia [12] . Histopathology reveals dense neutrophilic infiltrates in the dermis, and DIF is negative. This patient’s lack of fever and systemic symptoms rules out Sweet syndrome. Behcet’s disease is characterized by recurrent oral and genital ulcers, uveitis, and neutrophilic skin lesions such as pustules and nodular erythema [13] . Histopathology shows perivascular lymphocytic infiltration with vasculitis, and DIF demonstrates granular IgA deposition at the dermoepidermal junction. The absence of systemic mucocutaneous involvement excludes Behçet’s disease.

Given the presence of annular bullous lesions in this patient, differentiation from autoimmune blistering disorders is crucial [14] . Bullous pemphigoid (BP) typically presents with tense bullae on erythematous or urticarial plaques, associated with severe pruritus [15] . Histopathology shows subepidermal bullae with eosinophilic infiltration, and DIF reveals linear IgG and C3 deposition along the basement membrane. This patient’s negative BP180 and BP230 antibodies and DIF findings exclude BP. Dermatitis herpetiformis is characterized by grouped, pruritic vesicles and papules predominantly on extensor surfaces, often associated with gluten-sensitive enteropathy [16] . Histopathology shows subepidermal vesicles with neutrophilic microabscesses, and DIF demonstrates granular IgA deposition in dermal papillae. The absence of pruritus, gastrointestinal symptoms, and IgA deposition rules out dermatitis herpetiformis. Linear IgA bullous dermatosis (LABD) presents as clustered bullae in a “string of pearls” arrangement, frequently occurring in flexural areas. Histopathology reveals subepidermal blisters with neutrophilic infiltration, and DIF shows linear IgA deposition at the basement membrane [17] . This patient’s negative linear IgA antibody and DIF findings exclude this diagnosis.

There are no standardized treatment guidelines for RND, and management primarily focuses on controlling the underlying RA-related systemic inflammation. Glucocorticoids, such as prednisone (30 - 60 mg/d), provide rapid symptom relief. Immunosuppressive agents, including methotrexate, cyclophosphamide, hydroxychloroquine, leflunomide, and tripterygium wilfordii (thunder god vine), may be used in refractory cases [1] . Biologics such as rituximab and TNF-α inhibitors (e.g., etanercept) may be considered for severe or recurrent cases [18] . Unlike classic RND, bullous RND is characterized by dense neutrophilic infiltrates within both the upper and mid-dermis beneath bullae, indicating a key role of neutrophils in the pathogenesis of the bullous variant. Bullous RND shows a superior response to dapsone or colchicine, which may be considered as first-line treatment [19] . However, dapsone carries a high risk of severe adverse effects, such as hemolytic anemia, agranulocytosis, and dapsone hypersensitivity syndrome (DHS), necessitating pre-treatment genetic screening for HLA-B*13:01 and G6PD deficiency to prevent complications [20] . In contrast, colchicine is a safer alternative with proven efficacy, mild side effects, and affordability, and has shown therapeutic benefits in neutrophilic dermatoses such as Sweet syndrome and palmoplantar pustulosis. Its anti-inflammatory mechanism primarily involves inhibition of neutrophil activation and chemotaxis, making it a suitable alternative for patients intolerant to dapsone [21] .

This case highlights the diagnostic challenges of RND, particularly when bullous lesions are present, which can mimic other dermatologic conditions. The patient’s history of RA and interstitial pneumonia, along with high-titer RF and anti-CCP positivity, underscores the importance of correlating cutaneous findings with systemic disease. For dermatologists, recognizing RND as a cutaneous manifestation of RA can prevent misdiagnosis and ensure timely treatment, ultimately improving patient outcomes.

Rheumatoid neutrophilic dermatitis (RND) is a rare cutaneous manifestation primarily that primarily affects patients with active or severe rheumatoid arthritis (RA). Histopathological examination remains the diagnostic gold standard. As a diagnosis of exclusion, RND must be distinguished from other neutrophilic dermatoses and autoimmune bullous disorders. Management options include topical or systemic glucocorticoids, neutrophil-targeting agents such as dapsone and colchicine, as well as immunosuppressants and biologics. The choice of treatment depends on the severity of the disease and systemic involvement. For dermatologists, recognizing RND as a cutaneous manifestation of RA is crucial to prevent misdiagnosis and ensure timely treatment, ultimately improving patient outcomes.