SUN-781 Isolated Non-PTH-Mediated Hypercalcemia: A Rare Presentation of Sarcoidosis

Abstract Disclosure: C. Xue: None. A.M. Aviles Melendez: None. A. Yousef: None. M. Quartuccio: None. Background: Non-parathyroid hormone (PTH)-mediated hypercalcemia can result from various causes, including granulomatous diseases like sarcoidosis, which is associated with increased extrarenal 1-α-hydroxylase activity and excess production of 1,25-dihydroxyvitamin D (1,25(OH)2D). Here we present a case of sarcoidosis that exhibited a rare presentation of isolated non-PTH-mediated hypercalcemia, initially with normal 1,25(OH)2D levels and a false-negative core biopsy of a retroperitoneal lymph node. Clinical Case: A 44-year-old male with a history of hypertension and type 2 diabetes presented with malaise, polyuria, and polydipsia for 2 weeks. Laboratory tests showed severe hypercalcemia, with serum calcium of 16.4 mg/dL (N: 8.3-10.6 mg/dL) and low parathyroid hormone (PTH) at 7.3 pg/mL (N: 18-88 pg/mL). PTH-related peptide (PTH-rp), 25-hydroxy vitamin D (25(OH)D) (22 ng/mL, N: 20-50 ng/mL), 1,25(OH)2D (42 pg/mL, N: 18-64 pg/mL), thyroid stimulating hormone (TSH), and albumin were all normal. Bone survey was negative for osseous lesions, and chest X-ray showed no lymphadenopathy. He denied using thiazide diuretics or vitamin A supplements. He was treated with intravenous fluids, calcitonin, and zoledronic acid, which improved his calcium to 11.6 mg/dL before discharge. Three months later, he returned with similar symptoms and an elevated calcium level of 14.3 mg/dL, again with suppressed PTH. His 24-hour urine calcium was elevated at 719 mg (N: 50-300 mg). PTH-rp, 25(OH)D, and angiotensin-converting enzyme (ACE) levels were normal. Treatment with intravenous fluids, calcitonin, and zoledronic acid, lowered his calcium to 10.8 mg/dL. He was discharged on cinacalcet. During outpatient follow-up, his 1,25(OH)2D was found to be elevated at 84 pg/mL, and a computed tomography (CT) scan showed retroperitoneal lymphadenopathy. A core needle biopsy of the retroperitoneal lymph node showed benign lymphoid tissue. However, excisional biopsies of the liver, peritoneum, and retroperitoneal lymph node revealed non-necrotizing granulomatous inflammation. He was diagnosed with sarcoidosis and started on high-dose steroids, later transitioning to mycophenolate. With that treatment, calcium levels normalized quickly. Conclusion: The diagnosis of sarcoidosis can be challenging and presentation as isolated hypercalcemia without pulmonary involvement is very rare. Normal ACE and 1,25(OH)2D levels during initial hospitalization, along with false-negative results from the core needle biopsy, further complicated the diagnostic process. This case highlights the diagnostic complexities of non-PTH-mediated hypercalcemia and underscores the importance of a comprehensive workup, including medication review, lab tests, radiography, and biopsy, with consideration for excisional biopsy. Presentation: Sunday, July 13, 2025