Eosinophilic Fasciitis in a 78-Year-Old Man Following Pembrolizumab Treatment for Bladder Cancer.

BACKGROUND Immune checkpoint inhibitors (ICI) like pembrolizumab are increasingly used in cancer treatment and have become the standard of care for certain types of malignancies. Expanded use of these medications has led to more frequent recognition of immune-related adverse events (irAEs), including those presenting with sclerosing skin conditions such as eosinophilic fasciitis (EF). This case report describes the clinical presentation and management of a 78-year-old man with a history of bladder cancer who developed eosinophilic fasciitis after 6 months of treatment with an ICI. CASE REPORT Following 6 months of treatment with pembrolizumab, the patient developed capillary-leakage syndrome (CLS), which was treated with intravenous immunoglobulin (IVIG) and steroids. Several months after the resolution of his CLS, he developed painful hardening of the skin in his extremities and back, with notable induration of the skin and restricted range of motion across his elbows on physical examination. Laboratory workup revealed elevated inflammatory markers and eosinophilia. Skin biopsy revealed fibrosis of subcutaneous tissue and deep fascia, with multifocal collections of lymphocytes and plasma cells, consistent with eosinophilic fasciitis. Pembrolizumab was discontinued, and he received treatment with prednisone, mycophenolate mofetil, hydroxychloroquine, and benralizumab, with some improvement in his skin lesions. CONCLUSIONS This case report supports the need to have a high index of suspicion and investigate for eosinophilic fasciitis in cancer patients treated with anti-PD-1 medications who present with symmetric, painful hardening of the skin.