7635 Severe Osteoporosis in a Patient with Heterotopic Calcification: A Case Report

Abstract Disclosure: D. Salih Bacha: None. L.Z. Khan: None. Background: While osteoporosis and heterotopic ossification (HO) are distinct conditions affecting bone health, their coexistence poses intriguing clinical challenges. Osteoporosis, characterized by increased bone fragility, typically results from various factors such as aging, steroid use, or malabsorption. HO is a condition where bone forms abnormally in soft tissues. Risk factors that predispose to HO include male sex, spinal cord injury, trauma, surgery, and genetic factors. Treatment of HO is typically surgical resection and NSAIDs. Initial evidence supported the use of bisphosphonates for preventing ectopic bone formation post-trauma, but recent data failed to show significant benefit in HO prevention. This case presents a patient with unique challenges of both HO and bone fragility with multiple severe vertebral fractures. Case: A 44-year-old male patient had a major motor vehicle accident necessitating multiple recurrent abdominal surgeries. During one exploratory laparotomy, diffuse mesenteric calcifications were noted, indicative of HO. A baseline Dual X-ray Absorptiometry (DXA) scan revealed bone density of 1.003 g/cm2 and 0.788 g/cm2 at the spine and femoral neck, respectively, concerning for osteopenia. He was started on zoledronic acid in preparation for upcoming intestinal transplant. Few months after the transplant, he was started on daily tacrolimus and hydrocortisone for immunosuppression. Within months, he experienced sudden back pain while riding an elevator, and was found to have acute fractures in T8 and T9 vertebrae. A repeat DXA scan showed a further decline in bone density to 0.909 g/cm2 and 0.748 g/cm2 at the spine and femoral neck, respectively. Within a year, additional fractures occurred in the thoracic and lumbar spine (T10, T11, T12, L1, L2, L3, and L4), requiring multiple kyphoplasty interventions. Over time, worsening kyphosis, back pain, and height loss occurred, significantly affecting the patient's quality of life. He continued receiving yearly zoledronic acid infusions and underwent regular DXA scans, which revealed mild improvement in his bone density. Currently, there are no established guidelines specifying the optimal duration for bisphosphonate treatment in such cases. Therefore, our individualized treatment plan involves a tentative 10-year course of bisphosphonate treatment with yearly assessment of bone mineral density. Conclusion: Although the patient had some risk factors for osteoporosis, including daily steroid and tacrolimus use, the severity and frequency of his fractures suggested a potential synergy between osteoporosis and HO, where the formation of heterotopic calcifications may have been exacerbating his bone loss. The coexistence of osteoporosis and HO in this patient underscores the need for individualized care and establishment of treatment guidelines in patients with multiple bone disorders. Presentation: 6/3/2024