Phosphaturic Mesenchymal Right Hip Tumor with Tumor-Induced Osteomalacia as a Cause of Fall in a Nursing Home Resident

Phosphaturic mesenchymal tumors (PMT) are rare neoplasms recognized as an uncommon cause of osteomalacia and can present nearly anywhere in the body. Tumor-induced osteomalacia is a rare neoplastic syndrome defined by vitamin D deficiency and renal phosphate wasting. Given nonspecific symptoms and overall poor recognition, diagnosis of the tumor can be delayed for many years. We present a patient suffering from a rare form of oncogenic osteomalacia who was lost to follow-up and subsequently did not receive optimal care.

The patient is a 66-year-old Hispanic male with a past medical history of right hip PMT diagnosed in 2019, dementia, hypertension, seizure disorder, and stroke resulting in left hemiparesis who presented following a fall event that occurred at his nursing home facility in May 2023. Initial CT scan of the abdomen and pelvis revealed a sizable right iliac tumor with a destructive expansile mass arising from the medullary cavity of the right iliac bone with homogeneous enhancement. Tumor biopsy in 2019 revealed a mesenchymal tumor that was diffusely positive for vimentin and ERG markers, staining for mesenchymal tumor nuclei, leading to the diagnosis of paraneoplastic oncogenic osteomalacia. Endocrinology started the patient on vitamin D, phosphorus, and calcium supplementation upon initial diagnosis. Unfortunately, the patient was lost to oncology follow-up for several years. Repeat imaging at the time of the 2023 fall revealed that the tumor had grown significantly by 2000%. Surgical intervention was considered by orthopedic surgery, and an orthopedic oncologist was consulted. However, orthopedic oncology recommended nonoperative treatment since the patient was not an ideal candidate for a hemipelvectomy procedure and localized anesthesia given all his comorbidities and risk factors. The ultimate recommendation by both teams was palliative care with continued physical therapy, given the patient's poor performance status. Case management was arranged for hospice services, and the patient was discharged to his nursing home.

Our patient had presented ultimately due to complications secondary to PMT that was diagnosed three years prior to this hospitalization. PMT tumors can affect soft tissue or bone and overproduce fibroblast growth factor 23 (FGF-23), which reduces phosphate reabsorption and causes vitamin D deficiency. Due to the risk of pathological fractures in the older adult population, patients with hypophosphatemic osteomalacia should have a differential diagnosis of PMT. This case highlights a failure of safeguards for vulnerable populations, including the geriatric and cognitively infirm. This patient was incapable of independent care or possessing the mental faculties for self-advocacy. The patient was diagnosed within a reasonable time but did not receive curative therapy because of his comorbidities, with the expectation that he would receive optimal care with medical management. Given this patient's propensity for noncompliance, it is reasonable to assume that he would benefit from a more aggressive/curative approach to his condition. We appeal that populations vulnerable to indirect noncompliance should be managed with more aggressive/curative means if options are available.