Abstract: 【Abstract】 Objective To summarize the cutaneous manifestations, systemic involvement characteristics, and treatment outcomes of patients with skin-involved eosinophilic granulomatosis with polyangiitis （EGPA） . Methods A retrospective study was conducted on hospitalized patients diagnosed with EGPA at Huashan Hospital, Fudan University from August 2022 to April 2025. Data on demographic characteristics, skin lesion morphology, systemic involvement, laboratory findings, treatment regimens, and prognosis were collected. The relationship between antineutrophil cytoplasmic antibody （ANCA） phenotypes and eosinophilic tissue infiltration patterns was analyzed, and clinical outcomes were analyzed among patients receiving different treatments in the context of recently emerging targeted therapeutic strategies for EGPA. Results A total of 16 patients with EGPA were included, comprising 7 males and 9 females, with the age being 51.0 ± 17.0 years. The median diagnostic delay was 5.5 months. All patients exhibited cutaneous involvement, and 15 presented with persistent wheal-like lesions/edematous erythema as the initial manifestation; other skin lesions included purpura （6 cases）, subcutaneous nodules （4 cases）, and ulceration/necrosis （3 cases）. Systemic involvement commonly occurred in the ear, nose, and throat system （10 cases） and the lungs （7 cases）. Laboratory findings revealed peripheral blood eosinophilia and elevated interleukin-5 levels in all 16 patients. The ANCA positivity rate was low, with 4 patients testing positive for myeloperoxidase-ANCA （MPO-ANCA） and 12 testing negative. ANCA-positive patients predominantly exhibited a vasculitis-associated phenotype, including purpura, skin necrosis, and mononeuritis multiplex, whereas ANCA-negative patients more commonly presented with persistent wheal-like lesions, edematous erythema, and prominent eosinophilic tissue infiltration. Regarding treatment and outcomes, 15 patients achieved clinical remission or marked improvement after a median treatment duration of 7 months; during a median follow-up of 18 months, 1 patient experienced disease relapse during glucocorticoid tapering, while the remaining patients remained relapse-free. Notably, 2 MPO-ANCA-positive patients with refractory/severe EGPA achieved clinical remission after receiving systemic glucocorticoids combined with rituximab, and 4 non-severe EGPA patients with a high eosinophil burden achieved complete clinical remission following treatment with systemic glucocorticoids combined with mepolizumab. Conclusions In EGPA patients with cutaneous involvement, persistent wheal-like lesions/edematous erythema were the most common skin manifestations, and systemic involvement predominantly occurred in the ear, nose, and throat system and the lungs. In this study, ANCA-negative patients accounted for a relatively high proportion and exhibited prominent eosinophilic infiltration on histopathological examination. Overall, patients achieved favorable clinical outcomes following treatment with systemic glucocorticoids alone or in combination. A high index of suspicion for EGPA should be maintained when patients present with refractory urticaria-like rashes, peripheral blood eosinophilia, and comorbid asthma or sinusitis.

Key words: Vasculitis, Eosinophilic granulomatosis with polyangiitis, Antibodies, antineutrophil cytoplasmic, Rituximab, Mepolizumab