[Immune checkpoint inhibitor-induced eosinophilic fasciitis: a case report and literature review]

A 58-year-old male patient with angioimmunoblastic T-cell lymphoma developed a rash and skin tightness on the face, limbs, and trunk together with joint stiffness and dysfunction after 6 months of treatment with the programmed cell death protein-1 inhibitor camrelizumab. Laboratory tests revealed progressive eosinophilia over 6 months, with the eosinophil count increasing from 0.07×10⁹/L to 3.3×10⁹/L. Magnetic resonance imaging showed thickened skin of both forearms, while T₂-weighted imaging showed markedly increased signal intensity within the myofascia. Skin biopsy of the right forearm showed thickened and fibrosed fascia and infiltration of inflammatory cells, including lymphocytes, plasma cells, and eosinophils. The patient was diagnosed with immune checkpoint inhibitor (ICI)-induced eosinophilic fasciitis (EF). After beginning treatment with methylprednisolone (40 mg daily), methotrexate (10 mg/week), and baricitinib (4 mg daily), his symptoms of skin tightness and joint dysfunction significantly improved within 1 month, and his peripheral blood eosinophil count decreased to 0.17×10⁹/L. ICI-induced EF is a rare immune-related adverse reaction. To date, only 20 cases have been reported in published foreign literature, and their clinical characteristics are summarized here. The time from ICI treatment to EF was 12 (8,15) months, and the main clinical manifestations included skin involvement (n=19), joint dysfunction (n=11), myalgia/muscle weakness (n=9), and peripheral eosinophilia (n=16). After treatment, the clinical symptoms of EF improved in 17 patients, and eosinophil counts returned to normal after 3 (1,8) months. EF is a dysfunctional adverse response to ICI therapy. Tumor patients undergoing immunotherapy should be monitored for symptoms of EF. Early treatment is essential for preventing complications.