Immune checkpoint inhibitor‐induced eosinophilic fasciitis: A pharmacovigilance and EADV Task force study

BACKGROUND: With the widespread use of immune checkpoint inhibitors (ICI), rare cutaneous immune-related adverse events (cirAEs), including ICI-induced eosinophilic fasciitis (ICI-EF), are increasingly encountered. However, data on its clinical presentation and optimal therapeutic approaches remain sparse. OBJECTIVES: This study aimed to further characterize the clinical features and outcomes of ICI-EF. METHODS: This retrospective observational study analysed clinical features, treatment strategies and outcomes of ICI-EF cases from EADV Task Force-affiliated dermatology departments, complemented by cases from the current available literature and two international pharmacovigilance databases. Patient demographics, clinical characteristics, diagnostics, treatment and follow-up data were extracted from the medical records and databases. RESULTS: We present 121 ICI-EF cases from the EADV Task Force (n = 15), FPVD (n = 21), VigiBase® (n = 45) and the literature (n = 40). The most prevalent underlying malignancy in all groups was melanoma (50%), with PD-1 inhibitor monotherapy (81%) being the predominant offending drug class. The median time to ICI-EF onset was 10 months (IQR 6.8-16.3; range < 1-36). Detailed clinical information was available for 76 of the 121 cases (63%), revealing a highly variable clinical presentation. Treatment primarily involved ICI discontinuation (83%) and systemic corticosteroids (80%), followed by methotrexate (41%), intravenous immunoglobulins (12%) and mycophenolate mofetil (13%), resulting in the partial or complete resolution of ICI-EF symptoms (66%). CONCLUSIONS: ICI-EF is a rare heterogeneous cirAE with varying clinical features and significant morbidity. Early recognition and timely treatment are key to ensuring ICI continuation and preserve oncologic outcomes.