hyperphosphatemia, fibroblast growth factor receptor, fibroblast growth factor 23, calcification, Diseases of the endocrine glands. Clinical endocrinology, RC648-665

Background/Objective: Pemigatinib, a fibroblast growth factor receptor (FGFR) 1-3 inhibitor, is a novel therapeutic approach for treating cholangiocarcinoma when an FGFR fusion or gene rearrangement is identified. Although the most reported side effect of pemigatinib is hyperphosphatemia, tumoral calcinosis with soft tissue calcifications is not widely recognized as a complication. We report a case of patient with hyperphosphatemic tumoral calcinosis on pemigatinib. Case Report: A 59-year-old woman with progressive metastatic cholangiocarcinoma, despite receiving treatment with cisplatin and gemcitabine for 7 months, was found to have an FGFR2-BICC1 fusion in the tumor on next-generation sequencing. Pemigatinib was, therefore, initiated. Four months into the therapy, multiple subcutaneous nodules developed over the lower portion of her back, hips, and legs. Punch biopsies revealed deep dermal and subcutaneous calcifications. Investigations revealed elevated serum phosphorus (7.5 mg/dL), normal serum calcium (8.7 mg/dL), and elevated intact fibroblast growth factor-23 (FGF23, 1216 pg/mL; normal value