Nivolumab-Induced Fasciitis Mimicking Scleroderma: A Diagnostic Challenge.

A 74-year-old male on nivolumab for desmoplastic melanoma developed progressive skin tightening, woody induration, and restricted mobility, initially suggestive of systemic sclerosis. He lacked classic scleroderma features (e.g., Raynaud's, digital ulcers) but had eosinophilia (1100 cells/µL) and antinuclear antibody (ANA)/ ribonucleoprotein (RNP) positivity. MRI confirmed eosinophilic fasciitis (EF), prompting discontinuation of nivolumab and initiation of high-dose corticosteroids and mycophenolate, leading to gradual improvement over six months. This case highlights the diagnostic overlap between immune checkpoint inhibitor (ICI)-induced scleroderma-like syndrome and EF, emphasizing the need for early recognition and tailored immunosuppression to mitigate immune-related adverse events (irAEs) while balancing cancer therapy. Awareness of atypical presentations (e.g., hand/face involvement in EF) is critical for timely intervention.