8270 A Rare Case Of PTHrP Induced Severe Hypercalcemia Secondary To Squamous Cell Carcinoma Of Tongue

Abstract Disclosure: N. Vennelaganti: None. S. Vennelaganti: None. K. McCowen: None. Background: PTHrP-mediated hypercalcemia is often associated with solid organ malignancies and indicates a poor prognosis. The occurrence of this condition due to SCC of the head and neck, particularly of the tongue, is uncommon. This case report aims to shed light on this rare clinical presentation. Clinical Case: A 70-year-old woman with a history of tobacco use disorder, alcoholic liver cirrhosis, and a chronic fungal prosthetic joint infection presented with altered mental status and acute kidney injury. Laboratory tests revealed a corrected calcium level of 15.4 mg/dL and suppressed PTH of 3 pg/mL, indicating non-PTH-dependent hypercalcemia. Differentials considered included malignancy, multiple myeloma, 1,25 OH Vit D mediated hypercalcemia via fungal granuloma formation, and immobilization. Diagnostic evaluation revealed normal levels of 25 hydroxy Vitamin D ie: 54 ng/mL, normal kappa to lambda ratio suggestive of negative myeloma screen, normal TSH of 2.81 uIU/mL, and a low 1,25 OH Vit D level ie: 11.4 pg/mL (Ref range: 19.9-79.3 pg/mL). An elevated PTHrP concentration of 9.7 pmol/L (ref range 0-3.4 pmol/L) was noted. CT angiography performed for stroke evaluation incidentally discovered a base of tongue mass, which was difficult to appreciate on exam due to obtundation. A biopsy confirmed SCC of the tongue, and she was determined to be Stage IVA. The patient's hypercalcemia was determined to be secondary to PTHrP production from the tongue SCC compounded by immobilization. She was treated with IV fluids and subcutaneous calcitonin, normalizing her calcium levels over 20 days. IV Bisphosphonates were held inpatient due to poor renal function. She was seen by oncology and determined to not be fit for surgical management or chemotherapy. Radiation therapy was advised for management and patient was discharged. While awaiting her outpatient radiation treatment, the patient had another episode of altered mental status and was found to have a serum calcium of 16.4 mg/dL. She was managed with IV fluids, calcitonin and IV Zoledronate which improved her serum calcium. She has since been receiving monthly IV Zometa with oncology for hypercalcemia of malignancy. She was recently readmitted with severe oropharyngeal and pharyngeal dysphagia and has received a PEG tube for feeding. She is still pending radiation therapy for SCC tongue. Conclusion: Initially, during the workup of this case, we believed her hypercalcemia was likely immobilization-induced, but thorough investigation and the elevated PTHrP levels steered us towards malignancy as a potential etiology. This case is an example of an occult malignancy which lead to severe hypercalcemia. It also contributes to the understanding of hypercalcemia in cancer patients and highlights the rare association of SCC of the tongue with PTHrP-mediated hypercalcemia . PTHrP secreting SCC of head and neck are typically associated with a poor prognosis. Presentation: 6/2/2024