The Foot That Broke Both Hips: A Case Report and Literature Review of Tumor-Induced Osteomalacia

A Rare Case of Phosphaturic Mesenchymal Tumor Distal Femur in a Young Female

Introduction

Phosphaturic mesenchymal tumors (PMTs) are rare bone neoplasms with diverse clinical presentations, often posing diagnostic challenges.

Case Report

We describe the case of a 37-year-old female schoolteacher with a PMT localized in the distal femur. Diagnostic indicators included hypophosphatemia, hyperphosphaturia, elevated fibroblast growth factor-23 levels, and clinical symptoms of osteomalacia. Surgical management involved tumor resection and limb salvage surgery with a megaprosthesis. The post-operative period was uneventful, leading to a stable discharge. On follow-up, the patient showed no signs of recurrence, regained full ambulation, remained pain-free, and resumed teaching comfortably.

Conclusion

This case highlights the importance of considering PMT in patients with unusual clinical symptoms, accompanied by hypophosphatemia, hyperphosphaturia, and osteomalacia, and demonstrates successful surgical management, leading to a favorable outcome.

Tumor-Induced Osteomalacia- Like Syndrome with Rickets and Infantile Hepatic Hemangioendothelioma

Tumor-induced osteomalacia (TIO), a rare paraneoplastic syndrome is seen in association with the overproduction of fibroblast growth factor-23 (FGF-23) by certain mesenchymal tumors in adults. In children, these phosphaturic mesenchymal tumors produce features of rickets similar to TIO. This condition is characterized by elevated blood levels of FGF-23, low phosphate, low or normal active vitamin D, and high alkaline phosphatase. Though the removal of the tumor is curative; in cases where surgical resection is not possible, medical treatment is successful with phosphate and active vitamin D in the improvement of symptoms. The case of a child with features of rickets is presented here to illustrate the importance of identifying this rare condition and instituting appropriate intervention.

Tumor-Induced Osteomalacia: A Case Report

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome with a variable presentation. We present a case of a 55-year-old female who presented with pain in the bilateral hip region for the last two years. On routine biochemical evaluation, she was found to have hypophosphatemia with an X-ray of the bilateral hip region showing an acute stress fracture in the bilateral intertrochanteric region of the femur. An evaluation for the cause of hypophosphatemia revealed renal phosphate loss with low percentage tubular reabsorption of phosphate (% TRP) of 83% (reference range: 85-95%), with tubular maximum phosphate reabsorption per unit glomerular filtration rate (TmP/GFR) of 2.07 mg/dL (reference range: 2.5-4.5 mg/dL (0.67 mmol/L; range: 0.84-1.23 mmol/L)). Further evaluation revealed elevated levels of intact fibroblast growth factor, 445.7 pg/mL (reference range: 23-95 pg/mL). A 68-Gallium DOTA-1-Nal3-octreotide (DOTANOC) PET-CT revealed a focal increased tracer uptake with a lytic lesion at the lateral metaphyseal aspect of the proximal right tibia, suspicious of somatostatin receptor avid mesenchymal tumor, leading to the diagnosis of TIO. Definitive treatment with complete surgical excision of the tumor was done. Postoperatively, her phosphorus level was within the normal target range even without oral phosphate supplementation. While it is a rare condition, a proper and systemic workup can lead to timely diagnosis and management of this debilitating benign condition.

Phosphaturic Mesenchymal Tumor in the Proximal Femur Presenting as Tumor-induced Osteomalacia: A Case Report and Literature Review

Introduction

An uncommon medical disorder known as tumor-induced osteomalacia (TIO) is characterized by severe hypophosphatemia, renal phosphate wasting, and osteomalacia due to a tumor. TIO has recently been linked to a particular kind of tumor known as phosphaturic mesenchymal tumor (PMT). PMTs release phosphatonins, such as fibroblast growth factor-23 (FGF23), which elevates serum levels of FGF23, leading to phosphate wasting and osteomalacia. However, due to their infrequent occurrence and vague symptoms, such as bone pain, myopathies, arthralgias, fractures, and weakness, the diagnosis of PMTs is often delayed or misdiagnosed. In this case report, a rare case of PMT in the proximal femur resulted in TIO, and it highlights the long and difficult journey from symptom onset to correct diagnosis and successful surgical management.

Case Report

A 51-year-old woman endured persistent joint pain, muscle weakness, and fatigue for 2 years. Despite having no known health issues, she suffered from hip pain that spreads to her knees and ankles, and tingling and paresthesia in her legs, making it difficult to bear weight. She underwent surgery to remove a parathyroid adenoma, but unfortunately, her symptoms returned. Her magnetic resonance imaging revealed a lesion in her proximal femur, which was promptly removed. The tissue examination results verified the identity of the tumor as a PMT. The patient's phosphorus levels returned to normal and after a year of follow-up, she was able to resume normal daily activities, bear weight on the affected limb and showed no signs of the tumor recurrence.

Conclusion

Adult patients experiencing bone pain, progressive weakness, and multiple fractures with no family history of similar conditions should consider TIO as a potential cause. It is rare and often misdiagnosed and complete surgical removal of the tumor is the optimal treatment for TIO, resulting in the resolution of long-standing symptoms and biochemical abnormalities. Timely recognition, localization, and surgical removal of the tumor are crucial for symptom resolution and the restoration of normal bone mineralization.

Tumor-induced osteomalacia: a case report

Background

Tumor-induced osteomalacia is a rare, acquired paraneoplastic syndrome, including hypophosphatemia, high serum alkaline phosphatase, reduced active vitamin D, suboptimal bone mineral density, bone pain, fragility fractures, and muscle weakness.

Case presentation

We report a case of 74–year–old male of mixed ancestry with hypophosphatemia resistant to treatment despite optimal compliance, associated with profound reduction of bone mineral density and multiple nontraumatic fractures, including bilateral rib fractures, lower-thoracic (T11, T12) vertebrae, and two fractures involving the surgical and anatomical neck of the right humerus. We discuss an approach to identifying the underlying cause of hypophosphatemia associated with fragility fractures, and options for management of this rare condition.

Conclusion

Although rare, tumor-induced osteomalacia can be diagnosed if a logical stepwise approach is implemented. Surgery could be curative if the tumor is properly located and is resectable.

PHOSPHATURIC MESENCHYMAL HEEL TUMOR PRESENTING WITH TUMOR-INDUCED OSTEOMALACIA

Objective

To help clinicians identify and treat patients with tumor-induced osteomalacia (TIO) resulting from a phosphaturic mesenchymal tumor, mixed connective tissue variant (PMTMCT).

Methods

Describe the history, presentation, laboratory findings, diagnostic studies, treatment, and literature review.

Results

A 58-year-old female with no significant past medical history presents with ongoing multiple bone pain for years. She had a bone scan showing multiple focal areas of increased uptake involving bilateral ribs, distal right tibia, and left femoral neck, representing previously healed fractures. Her bilateral lower-extremity magnetic resonance imaging showed stress fractures of the anteromedial cortex, right tibia, and the left femoral neck. Phosphorus was noted to be 1.9 mg/dL (normal range, 2.0 to 4.0 mg/dL), and alkaline phosphatase was 179 U/L (normal range, 25 to 110 U/L). Tubular maximum re-absorption of phosphate to glomerular filtration rate ratio was 0.438, which was low. An outside physician initiated patient on teriparatide, which showed bone mineral density improvement after 1 year, and then the teriparatide was stopped. Later, she developed a nontraumatic pubic ramus fracture; teriparatide was resumed. While on teriparatide, she developed several new rib fractures. Due to declining phosphorus levels, further investigation led to an elevated fibroblast growth factor 23 (FGF-23) level of 243 RU/mL (normal, <50 RU/mL). TIO was strongly suspected, and a nuclear medicine positron emission tomography/computed tomography trunk with ⁶⁸Ga-1,4,7,10-tetraazacyclododecane 1,4,7,10-tetraacetic acid tyrosine-3-octreotate (i.e., ⁶⁸Ga-DOTATATE) showed a right heel soft-tissue nodule. Fine-needle aspiration biopsy was performed, confirming PMTMCT, positive for FGF-23 mRNA. After surgery, her symptoms resolved and her phosphorus normalized.

Conclusion

TIO is a rare paraneoplastic syndrome characterized by bone pain, muscle weakness, and fractures associated with persistent hypophosphatemia. Clinicians now have new imaging tools to help identify and treat patients with PMTMCT.