A case of acute febrile neutrophilic dermatosis characterized with annular pustules

Dear Editor, A 62-year-old male developed an abrupt onset of painful erythematous plaques with annular-distributed pustules on the shoulder. Three days later, the rash spread to the whole body with fever of 38.7°C [Figure 1a]. He had a history of type 2 diabetes and cardiovascular disease for 2 years. The patient had no preceding infection history before onset of the disease.Figure 1: Clinical images: (a) Pustules arranged in annular pattern with scabs in the center, a "string-of-pearls" configuration. Clinical presentation after 10 (b) and 25 days (c) of treatment.Clinical examination showed multiple erythematous plaques and annularly distributed pustules, with exudation and scabbing in the center, on the shoulder, back, face, and scalp, and scattered around the limbs. Laboratory examination revealed a neutrophil proportion of 73.6% (reference range: 40%–75%), C-reactive protein of 59.61 mg/L (reference range: 0 mg/L–8 mg/L), and erythrocyte sedimentation rate of 25 mm/h (reference range: 0 mm/h–15 mm/h). Pathogenic biology-related tests such as bacterial culture, treponema pallidum antibody, HIV antibody, immune indexes such as anti-nuclear antibodies (ANA) and extractable nuclear antigens (ENA), and tumor markers such as carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) were all within normal ranges. Skin biopsy showed obvious edema of the upper dermis, diffuse lymphocytic infiltration, and some neutrophils in the superficial and middle layers of the dermis [Figure 2]. The symptoms, rash presentation, laboratory test, and skin histopathology result indicated acute febrile neutrophilic dermatosis. Oral minocycline 50 mg twice daily along with topical steroid and antibiotic ointment was prescribed. Ten days later, his pustules subsided, and erythema improved, and the pain was alleviated [Figure 1b]. All the rashes were almost clear after 25 days [Figure 1c], and no recurrence in the next 6 months. Subsequently, the medication was discontinued approximately after about 2 months of onset, during which no recurrence of the condition occurred. Currently, follow-up is still ongoing.Figure 2: Histopathologic images photomicrograph of a hematoxylin–eosin-stained section showed obvious edema of the upper dermis, diffuse lymphocytic infiltration, and some neutrophils in the superficial and middle layers of the dermis. (a: ×40; b: ×100).Acute febrile neutrophilic dermatosis, also known as Sweet's syndrome (SS), typically presents with tender erythematous plaques in an asymmetric distribution.[1] Pustular, bullous, or targetoid lesions are relatively rare. Lesions commonly appear on upper extremities and could also occur on the face, neck, back, and lower extremities. Simultaneously, SS patients might exhibit fever, arthralgia, eye inflammation, headache, and, on rare occasions, oral or genital involvement.[2] Nevertheless, atypical lesional presentation and relatively normal laboratory results could also occur in SS patients.[3] Even our patient exhibited distinct erythematous plaques, with annular pustules and scabs in the center, which could be quite challenging for a prompt and accurate diagnosis. As far as we know, this unique lesional manifestation is the very first to be reported. Histopathological examinations are the key diagnostic tool for confirming SS. Studies have shown that the composition of infiltrating cells depends on the developmental stage of the skin disease. In a study targeting SS patients undergoing sequential biopsies, the initial lymphocytic stage was followed by neutrophilic and then histiocytic infiltrates.[4] In early stages, some lymphocytes may appear, especially in cases related to myelodysplastic syndrome.[5] Given the complexity and variability of SS, it is recommended to perform skin biopsies at multiple time points throughout the disease course, ensuring sampling depth that extends to the subcutaneous fat layer. The diagnosis of SS includes major and minor criteria. Our patient met two major criteria and two minor criteria, and thus, the diagnosis of SS is confirmed.[2] Usually, SS has a high degree of steroid responsiveness and self-limitation. Due to the atypical presentation of symptoms, various diagnoses were suspected, and therefore, all possible laboratory tests and skin pathology were performed. However, before the diagnosis of SS, routine blood test revealed elevated neutrophils, and hence, we decided to treat the patient with minocycline rather than opting for other options. Minocycline not only has antimicrobial activity but also has anti-inflammatory action, as it reduces neutrophilic chemotaxis and inhibits the effect on proinflammatory cytokines. Since the patient started improving, we instructed him to continue with oral minocycline even though minocycline might induce SS, but it did not apparently in this case. In addition, the efficacy of novel agents, such as tumor necrosis factor-alpha inhibitors, interleukin-1 (IL-1) receptor antagonists, IL-6 inhibitors, and Janus kinase (JAK) inhibitors, has been reported in case reports.[6] The targeted therapy using biological agents and small molecule drugs offers new hope to patients, but their safety and efficacy still require further clinical research for validation. The diagnosis and treatment of SS is complicated. Thus, it is essential to know the various manifestations and histopathology characteristics of SS to make an accurate diagnosis and give proper treatment. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Data availability statement Data sharing not applicable to this article as no datasets were generated or analyzed during the current study. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.