A hidden tumor was slowly breaking this man's bones

Over the course of seven years, the man had been growing progressively weaker, which doctors initially attributed to small-fiber neuropathy and chronic Lyme disease. However, treatments including intravenous immunoglobulin and antibiotics failed to help. Over time, the man's condition worsened so much that he spent nine months largely confined to bed before seeking care for sharp chest pain that worsened when he breathed.

When the man arrived at the hospital, imaging revealed the full extent of the damage: long-standing fractures in both of his hips, an additional fracture in his left thigh bone, and 11 broken ribs on the right side of his chest. Doctors also discovered that these fractures weren't new injuries but instead signs of bones that had become dangerously fragile.

Eventually, doctors traced the problem to a rare condition called tumor-induced osteomalacia, caused by a small, 15x9 millimeter, slow-growing tumor lodged in his femur.

These tumors, known as phosphaturic mesenchymal tumors, are typically benign. However, they release excess amounts of a hormone-like substance that disrupts how the body handles phosphate, a mineral essential for keeping bones strong. Once phosphate levels drop too low, bones soften and weaken, making them prone to fractures even during everyday movement.

In this case, lab tests showed that the man's phosphate levels were dangerously low. In addition, his body was producing less active vitamin D than normal, further limiting his ability to rebuild bone. At the same time, levels of a protein called FGF23 were abnormally high, explaining why the man's kidneys were flushing phosphate out of his system rather than conserving it.

Why diagnosis took years

Diagnosing the condition had taken years. Symptoms like muscle weakness, fatigue, and bone pain are common to many disorders, and phosphate levels are not routinely checked in standard blood tests. As a result, these tumors are initially misdiagnosed in up to 95% of cases.

In this patient's case, the COVID-19 pandemic also played a role. For three years, the man relied heavily on telehealth visits, which meant that "nobody was able to appreciate how progressive his weakness had become," said Laura Glick, also of Harvard and MGH, who coauthored the case report.

A year after the surgery, the man was walking around the block with a single cane, accompanied by his grandchild, and reported far less pain.

The case highlights how easily tumor-induced osteomalacia can be missed. Studies show that almost all patients experience repeated fractures, most report widespread pain, and half develop significant weakness, yet diagnosis is often delayed for years. These tumors are small, rare, and can appear almost anywhere in the body, which makes them difficult to find without targeted testing.

When surgery isn't possible, treatment options include phosphate and vitamin D supplementation or a targeted drug that blocks the effects of FGF23. But when the tumor can be removed completely, recovery is often quick.

According to Glick, the broader lesson is about paying attention when symptoms don't add up.

"The most important message is to listen to your patients, even if every lab is stone-cold normal," she said. "Patients know themselves the best. If they come to you with progressive weakness or feeling 'off,' then chances are, they warrant additional work-up and testing."