Tumor-induced osteomalica is a rare paraneoplastic syndrome resulting from the increased excretion of phosphate salts in the urine. They are usually caused by benign mesenchymal tumors, such as a sarcoma.
As the phosphate salt level drops, the patient starts to suffer from muscle pain, bone pain, and fatigue, often leading to weakened bones and fractures.
The condition can usually be stopped by removing the tumor causing the condition. However, the tumor can often be very difficult to locate.