6785 Thrombocytopenia: A new adverse effect of Romosozumab

Abstract Disclosure: S. Dejhansathit: None. N. Akabogu: None. B. Stanley: None. F. marium: None. E.M. Bazuaye: None. L.S. Krusniak: None. U.Z. Khan: None. Introduction: Romosozumab, a monoclonal anti-sclerostin antibody, is a new anabolic agent approved by the US FDA in 2019 for treatment of osteoporosis. Osteocytes produce sclerostin which inhibits bone formation. Consequently, suppressing sclerostin enhances osteoblast function leading to improved bone mass and reduction in fractures. Romosozumab therapy has demonstrated efficacy in lowering vertebral and nonvertebral fractures. Despite its effectiveness, cardiovascular events are the main concern and it is contraindicated in individuals with prior history or increased risk of myocardial infarction or stroke. This case marks the first incidence of immune thrombocytopenia (ITP) associated with Romosozumab use. Case Description: A 72-year-old Caucasian woman with a past medical history of chronic kidney disease, GERD, seizure disorder, and asthma was referred to Endocrinology clinic for osteoporosis management. Osteoporosis was diagnosed in 2019 on DXA scan showing T-scores at lumbar spine (LS), femoral neck, and total hip as -3.1, -3.1, and -3.0, respectively. She was treated with Zoledronic acid injections. Workup at this visit showed elevated parathyroid level, while calcium, vitamin D, magnesium, phosphorus levels were within the normal range. Repeat DXA in February 2023 revealed a 4.8% decreased in BMD at LS. Due to severity of osteoporosis, treatment with Romosozumab monthly was initiated. After receiving the third dose of Romosozumab, she experienced epistaxis and easy bruising of her skin. Labs revealed severe thrombocytopenia (platelet count of 12,000/microL). Peripheral blood smear showed no platelet clumping or megakaryocytes. HIV and HCV testing returned negative, prompting a referral to hematology. A presumptive diagnosis of ITP was made. Treatment with prednisone was initiated. A careful history and review of medications was conducted for identification of secondary causes of thrombocytopenia. Romosozumab was the only medication added recently, leading to a suspicion that it might be the causative factor for thrombocytopenia. Consequently, Romosozumab was discontinued. Subsequent complete blood count revealed a return of the normal platelet count. Conclusion: Given the novelty of Romosozumab, limited data exist on its safety profile. This case marks the first reported incidence of thrombocytopenia associated with Romosozumab use underscoring the importance of identifying drugs as a secondary cause of thrombocytopenia. This case emphasizes the need for ongoing pharmacovigilance and monitoring when using novel therapeutic agents like Romosozumab. Presentation: 6/3/2024