SAT-784 - A Case of Intravenous Bisphosphonate-Induced Orbital Inflammation

Introduction: Androgen deprivation therapy (ADT) in men with prostate cancer is associated with decreased bone mineral density and increased fracture risk. Baseline bone density measurement is recommended in all men initiating ADT, and osteoclast inhibitors are first-line therapy in those with osteoporosis. We present a case of optic perineuritis following intravenous (IV) zoledronic acid administration.

Case Presentation: A 57-year-old man with prostate cancer diagnosed in 2021 presented in 2022 for evaluation of osteoporosis while receiving ADT. A DEXA scan in 2022 demonstrated T-scores of -2.4 at the lumbar spine and -2.5 at the left femoral neck. He was started on denosumab in 2022 and continued therapy through 2024. ADT was discontinued in 2023. Due to loss of insurance coverage of denosumab after completion of ADT, he received one dose of IV zoledronic acid in 2025 to stabilize bone mineral density. One week later, he developed left eye swelling, scleral erythema, and pain, and was treated with prednisone eye drops. After two days of treatment, he developed left eye photopsias and presented to the hospital. MRI of the orbits revealed left eye edema of the retro-orbital fat, mild proptosis, and enhancement of the optic nerve sheath, consistent with optic perineuritis. He was diagnosed with bisphosphonate-associated acute orbital inflammation and treated with one dose of IV methylprednisolone followed by an oral prednisone taper. His eye pain, orbital swelling, and scleral injection have improved, but his left eye vision has not returned to baseline.

Discussion: This patient was found to have IV bisphosphonate-induced orbital inflammation. He was treated with corticosteroids and demonstrated clinical improvement, but continues to have visual deficits. Both IV and oral bisphosphonates can cause ocular toxicity, including uveitis, scleritis, and conjunctivitis. Although rare, the risk of ocular inflammation is higher with IV bisphosphonate therapy than oral therapy. The 1-year incidence of ocular complications is 1.73% for dry eyes, 0.97% for corneal and surface inflammation, and 0.17% for uveitis. Ocular inflammation related to IV bisphosphonates typically occurs within days of infusion. Oral bisphosphonate–associated inflammation may present up to two to three weeks after initiation. Patients with ocular symptoms should be promptly referred to ophthalmology. The prognosis is generally favorable when treated appropriately, and delayed diagnosis and treatment can lead to irreversible vision loss. Clinicians should consider obtaining a CT or MRI of the orbits for patients presenting with eye pain within two weeks of bisphosphonate therapy. The mainstay of therapy includes topical corticosteroids and cycloplegic agents. Cessation of the offending drug is recommended. Awareness of this rare adverse effect is essential to ensure timely diagnosis and appropriate management.

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