Bone fragility in a post-intestinal transplant patient with mesenteric heterotopic ossification

Heterotopic ossification (HO) is the aberrant formation of mature lamellar bone in extraskeletal tissues, most commonly following trauma or surgery. Mesenteric involvement is rare and often discovered incidentally. We report the case of a 44-yr-old man with mesenteric HO in the setting of multiple emergent abdominal surgeries after a motor vehicle accident. Histopathology confirmed bone with cartilage and BM within the mesentery. He subsequently required an isolated small-intestinal transplantation for short gut syndrome. Following transplantation, the patient developed multiple vertebral compression fractures in the setting of bone fragility due to chronic antirejection medications and high-dose steroid use. He received more than a decade of treatment with zoledronic acid, with stabilization of BMD and no additional fractures. He was later transitioned to denosumab. This case underscores the rarity of HO occurring in the mesentery and highlights the challenges of managing bone fragility in high-risk post-intestinal transplant patients. This case highlights the importance of monitoring and managing bone fragility in patients undergoing intestinal transplantation and long-term immunosuppressive therapy.