SUN-802 Hypercalcemia of Malignancy in Pregnancy

Abstract Disclosure: Y. Gao: None. M. Aziz: None. P. Kishore: None. Introduction: Approximately 5% of individuals infected with Human T cell lymphotropic virus -1 (HTLV-1) develop a hematologic malignancy called Adult T-cell Leukemia/Lymphoma (ATLL). Around 50-70% of patients with ATLL will develop hypercalcemia at some point in their disease course. This is the highest among hematologic malignancies. Here, we present a case of a pregnant patient with severe hypercalcemia due to ATLL. Case: A 42-year-old pregnant female at 31 weeks of gestation with no past medical history presented to the hospital for a diffuse pruritic rash. Labs were remarkable for calcium 18.3mg/dL (8.5-10.5mg/dL), PTH 5.4pg/ml (20.0-80.0pg/mL), Vitamin D 1,25-dihydroxy 24.0pg/mL (18-72pg/mL), and PTH-rP 28pg/mL (11-20pg/mL). Ten days before admission the calcium was 10.2mg/dL. The initial diagnosis was crusted scabies, but a mineral oil scrape did not reveal scabies. The concern for scabies led to the evaluation of possible immunodeficiency for which HTLV-1 viral load was checked and was elevated to 2,200,000 copies/mL (undetectable). CT scan of the chest showed bilateral axillary lymphadenopathy and a prominent mediastinal soft tissue mass. Skin biopsy showed an atypical epidermotropic lymphocytic infiltrate which was consistent with a T-cell lymphoma and the patient was diagnosed with ATLL. To avoid using bisphosphonate in pregnancy, hypercalcemia was initially treated with IV fluids and calcitonin with the improvement of calcium to 12.4mg/dL. Severe hypercalcemia recurred shortly after the completion of the calcitonin course. After the risks and benefits of bisphosphonate use in pregnancy were discussed with the patient, zoledronic acid 4mg was administered, which reduced calcium to 9.6mg/dL in three days. She underwent a cesarean-section at 32 weeks and delivered a baby boy who had hypocalcemia for the first ten days of life. During her prolonged hospital course, she developed recurrent hypercalcemia, refractory to zoledronic acid but responsive to denosumab. Conclusion: Hypercalcemia due to ATLL is multifactorial in etiology. Production of RANKL by neoplastic T-cells is the most significant mechanism but PTH-rP production can also contribute. This patient had a mildly elevated PTH-rP which may be normal in pregnancy due to its production by the placenta and breasts. Therefore, it would be incorrect to attribute her hypercalcemia solely to PTH-rP. This case also suggests that denosumab may offer a more lasting resolution of hypercalcemia from ATLL rather than zoledronic acid. Denosumab is more effective likely due to its ability to directly antagonize the underlying mechanism of RANKL-mediated hypercalcemia in ATLL. Finally, this case highlights one of the known side effects of bisphosphonate use in pregnancy which is neonatal hypocalcemia. Presentation: Sunday, July 13, 2025