Oncogenic osteomalacia associated with a mesenchymal chondrosarcoma

Area of Science:

• Endocrinology
• Oncology
• Bone Metabolism

Background:

• Phosphaturic osteomalacia is a rare condition characterized by impaired bone mineralization and excessive phosphate excretion.
• This case presents a patient with phosphaturic osteomalacia lacking typical signs of hyperparathyroidism.

Observation:

• The patient showed partial improvement with vitamin D and phosphate therapy, but persistent phosphaturia.
• Surgical removal of a mesenchymal chondrosarcoma from the foot led to rapid resolution of phosphaturia and osteomalacia.

Findings:

• Preoperative and postoperative vitamin D metabolite levels did not explain the observed changes in phosphate excretion.
• Post-tumor removal, urinary cyclic adenosine monophosphate (cAMP) and bone histology normalized within a year.

Implications:

• This case suggests that certain tumors can secrete factors causing non-parathyroid mediated phosphaturia.
• The findings indicate a potential paraneoplastic syndrome involving phosphate wasting, independent of vitamin D metabolism alterations.