MON-780 Persistent Hypercalcemia and Parathyromatosis: Insights from a Rare Decade-Long Clinical Case

Abstract Disclosure: L. Li: None. D. Saba: None. J. Vu: None. Parathyromatosis presents a rare and challenging condition in managing recurrent primary hyperparathyroidism and persistent hypercalcemia after parathyroidectomy. As of 2022, fewer than 40 cases have been reported in the English-language medical literature. This condition often arises from the intraoperative dissemination of hyperfunctional parathyroid tissue during initial surgeries.We present the case of a 63-year-old woman diagnosed with hyperparathyroidism in 2005, for which she underwent a left superior parathyroidectomy. Despite this, her condition recurred in 2015, with rising calcium and parathyroid hormone (PTH) levels, prompting further surgical interventions. Over the next 8 years, she underwent five additional surgeries, including a partial right lower thyroidectomy, right cervical thymectomy, left thyroid lobectomy, and extensive neck muscles dissections to manage her recurrent hyperparathyroidism and hypercalcemia. While each surgery initially appeared promising, follow-up PTH levels and biopsies consistently revealed ongoing parathyromatosis. This case highlights the complexity of diagnosing and managing parathyromatosis, both surgically and medically. Surgical interventions are further complicated by the difficulty in precisely localizing disseminated parathyroid tissue. Imaging modalities such as sestamibi scans, 4D CT, MRI, and F-18 fluorocholine PET failed to accurately localize likely due to the small size of the lesions and their fusion with surrounding tissues. Selective venous sampling for PTH levels provided useful information about regions of hyperactivity, but did not lead to curative treatment. Medical management of her persistent hypercalcemia was equally challenging. Treatments such as Cinacalcet and Denosumab were not viable due to her adverse reactions, limiting pharmacological options. Intermittent zoledronic acid infusions and hydration therapy offered temporary relief but did not address the underlying hyperparathyroidism, leaving her at continued risk for hypercalcemia-related complications.Overall, this case contributes to the growing body of literature on parathyromatosis and emphasizes the significant challenges in its management. It highlights the limitations of current surgical techniques, imaging modalities, and medical therapies. The need for a multidisciplinary approach, involving surgeons, endocrinologists, and radiologists, is crucial for optimizing outcomes. Future research should focus on improving detection and treatment methods for disseminated parathyroid tissue and refining surgical approaches to prevent parathyromatosis after initial parathyroidectomy. Presentation: Monday, July 14, 2025