Immune checkpoint inhibitor-related eosinophilic fasciitis: 3 case reports with literature review.

Introduction: Immune checkpoint inhibitors (ICIs) are associated with a large spectrum of immune-related Adverse Events (irAEs). ICIs can exceptionally induce eosinophilic fasciitis (EF). Data of ICI-related EF (ICI-EF) are scarce without clear guidelines on both diagnosis and treatment.

Methods: We conducted a literature review of all cases of patients over 18 years old with EF diagnosis following ICI treatment between 2016 and November 2023 and meeting Pinal-Fernandez's criteria. New cases from two departments (French Region of Occitania) were added to complete the cohort.

Results: We selected 30 cases: 27 from literature review and 3 new cases diagnosed in Occitania. There was male predominance, with a sex ratio (M/F) of 1.3 with a median age of 57 years. The most common tumor was melanoma (50%). The time to onset was 10 months. Twenty-two patients (73%) had hypereosinophilia (mean 3300/mm³). A large majority (25/30, 83%) received at least one course of steroids therapy while immunosuppressive treatment was needed for 18 patients (72%). Rechallenge was proposed in 2 patients without recurrence of EF.

Discussion: Clinical and biological characteristics appeared roughly similar between ICI-EF and idiopathic-EF. Management is currently based on clinical practice of idiopathic-EF with corticosteroids often used in first line of treatment. However, a second line (methotrexate of mycophenolate mofetil) was required in majority of patients as observed in idiopathic-EF.

Conclusion: There is a significant reporting signal of EF following ICIs. A proactive management is required in all cases. A specific algorithm for treatment is finally proposed.