Dorsal vertebral body tumor and non-compressive quadriparesis – A rare case report of a phosphaturic mesenchymal tumor

BACKGROUND: Phosphaturic mesenchymal tumors cause renal phosphate wasting leading to hypophosphatemia manifesting as bone pain and fractures. About 95% of these tumors involve the extremities and the appendicular skeleton, with spinal tumors being exceedingly rare. We describe a case of non-compressive quadriparesis, caused by a thoracic vertebral body phosphaturic mesenchymal tumor (PMT). CASE DESCRIPTION: A 34-year-old gentleman presented with a 3-year history of gradually progressive quadriparesis, predominantly involving proximal muscles. Magnetic resonance imaging neither showed evidence of compressive lesions nor myelopathy. On routine biochemistry, he was found to have hypophosphatemia and phosphaturia, with serum phosphorus levels of 1.84 mg/dl, and fractional excretion of phosphorus >5%. A DOTATOC positron emission tomography scan suggested the possibility of a PMT in the D10 vertebral body with a corresponding hyperdense/sclerotic focus on non-contrast computed tomography. After instituting phosphate replacement therapy and complete surgical excision of the hyperdense focus, he made a full neurological recovery. His phosphate levels normalized without the need for supplements. Histopathological examination showed spindle cells with positive staining for Vimentin, a mesenchymal cell marker. At 5 years of follow-up, the patient continues to be asymptomatic with a full return to normal function and no residual weakness. CONCLUSION: PMTs involving the spine are a rare reversible cause of non-compressive quadriparesis. Early diagnosis and excision of the lesion correct the hypophosphatemia and result in complete neurological recovery.