Calcinosis Cutis With Selective Fibroblast Growth Factor Receptor Inhibitors: A Case Report and Review of Literature.

Selective fibroblast growth factor receptor (FGFR) inhibitors are emerging and promising treatment options in oncology, currently approved for metastatic cholangiocarcinoma and urothelial carcinoma. These agents are associated with various adverse events, including a range of dermatologic toxicities. In rare cases, they can cause calcinosis cutis (calcium deposition in the skin and subcutaneous tissue) or calciphylaxis (calcium deposition in blood vessels). Hyperphosphatemia, a common side effect, is considered a predisposing factor for these conditions. We report a rare case of pemigatinib-induced calcinosis cutis in a 46-year-old woman with FGFR2-TFAP2D fusion-positive metastatic cholangiocarcinoma. Ten days into treatment with pemigatinib, she developed painful, pruritic, erythematous leg lesions. Labs showed hyperphosphatemia with normal calcium; biopsy confirmed calcinosis cutis. Discontinuation of pemigatinib, phosphate binder therapy (calcium acetate), and topical steroids (triamcinolone) led to symptom resolution. We also review 10 similar cases linked to selective FGFR inhibitors, highlighting clinical features, management, and outcomes. Although rare, these conditions can be serious and potentially debilitating. Early recognition, regular phosphate monitoring, prompt intervention, drug adjustment or discontinuation, electrolyte correction, and wound care are key to improving patient outcomes.