Skip to main content


Posted by on Monday, September 9, 2019 in Fall 2019, Features, Homepage Highlights .

David Covington didn’t want to leave behind his hometown of Iowa City to move to Nashville, but when his wife, Natalie, wanted to follow her PhD adviser to Vanderbilt University School of Medicine and continue her education in Tennessee, Covington supported her.

Little did he know then the move might dramatically alter the fate of his health.

Shortly after the couple packed up their belongings and headed south in July 2016, Covington noticed unusual symptoms. He was having trouble keeping up while walking, had mild pain in his lower back and felt a noticeable discomfort and weakness throughout his body.

“We went back to my parents’ house in Iowa for Thanksgiving that year, and I was trying to mow their lawn, and I couldn’t get the lawnmower started,” said Covington.

A high school history and psychology teacher at East Nashville Magnet High School, Covington was only 26 and had no prior medical conditions.

As soon as the symptoms became concerning, he scheduled an appointment with a local orthopaedist, who diagnosed him with a degenerative disk in his lower back and referred him to physical therapy. Several rounds of therapy proved unsuccessful, and his pain was worsening.

Covington saw a second orthopaedist, whose X-rays discovered fractures in his hips. He was told the fractures were only slight and should heal themselves.

As the pain intensified, he saw a rheumatologist, who, after six months of careful watching, diagnosed him with psoriatic arthritis. Covington underwent several months of treatment only to find that a marker in his blood that should have decreased dramatically had only increased.

In less than two years, what began as proximal weakness in his abs and hips turned into an unexplained inability to walk.

“Honestly, I thought I was crazy and that it was all in my head. It was really hard for my wife and me,” said Covington, who had become so weak he began falling, causing more fractures throughout his body. With fractures in his ribs, ankles and femur, his condition limited his teaching abilities to his chair for the 2017-2018 school year, and he had to roll himself around the room to hand out papers. His weak state also caused him to fall in front of his class.


Diagnosing a rare disease

When Covington was referred to Kathryn Dahir, MD, an endocrinologist at Vanderbilt University Medical Center, at the end of March 2018 — almost two years after his symptoms began — he was ready for answers.

“By the time I got to Dr. Dahir, I was just ready to get a diagnosis of some sort. She was really comforting, because she would write everything down on a sheet of paper while she was talking to us and explain it all. For the first time, I felt like there was an appropriate level of confidence,” said Covington.

Kathryn Dahir, MD. Photo by Joe Howell.

“What was interesting about David was that he was a young, otherwise healthy man who had become progressively and rapidly disabled. His degree of disability was profound for somebody of his age,” said Dahir. “He was someone who required the use of assistive walking devices to even come into clinic, and he had so much proximal weakness that he couldn’t get up on the exam table by himself.”

Dahir recognized that symptoms this severe meant something unusual was likely happening with Covington’s bone metabolism. She ran a series of blood tests to check his levels of phosphorous and FGF23 — a hormone normally made by bone cells to regulate phosphorous levels, preventing an excess. Covington showed a relatively low phosphorous level and an elevated level of FGF23, hinting that a tissue other than bone may have been inappropriately depleting phosphorous.

Because bones are made from a mix of calcium, phosphorous and magnesium, low levels of phosphorous cause the skeletal matrix to become soft, leading to fractures and causing pain in the affected bones. The condition is known as osteomalacia.

From her extensive experience in endocrinology, Dahir knew that a possible cause of osteomalacia is a small benign tumor hiding somewhere in the body, typically in the hands, feet or nasal cavities. Known as tumor-induced osteomalacia (TIO), the condition is rare, and each case is often a medical mystery unto itself.

A PET scan confirmed Dahir’s suspicions — a small section the size of the tip of a pinky finger lit up in Covington’s brain directly under his temporal lobe, indicating a mass. The tumor’s location caused Dahir to think twice about TIO being the correct diagnosis.

“Here, you have a really rare disease in and of itself coupled with the rarest place you can find a tumor like this,” said Dahir.

No matter where the tumor is located, it can have the same effect on the bones. Dahir referred Covington to Reid Thompson, MD, William F. Meacham Professor of Neurological Surgery and chair of the department, for a second opinion.

“Dr. Dahir sent me a message saying, ‘I have a patient who I think may have TIO and has an intracranial mass. Would you see him?’ I had never heard of TIO,” said Thompson.

Despite his opinion that Covington’s condition was outside the realm of anything a neurosurgeon would ever see, Thompson visited with Covington less than a week later. A brief look at his MRI convinced him that Covington’s tumor was nothing more than a benign meningioma — a condition that encompasses roughly 90% of the patients Thompson sees in his clinic. Because they are benign, many meningiomas may be safely monitored without surgery.

“My thought was that I’d go into David’s room and say, ‘This looks like a meningioma to me. We’re not going to do an operation to take out this small benign tumor because that’s invasive brain surgery. We’ll do another MRI in six months like we do with other patients with incidentally discovered meningiomas.’

“But, something stopped me before I went into the room,” said Thompson.


Right place, right time, right spouse

Acknowledging his lack of understanding about TIO — the presumed diagnosis Dahir had sent over with Covington’s case — Thompson and a resident Googled the condition. The search only yielded three or four articles.

“The synopsis was that these tumors can masquerade as meningiomas and occur in the skull base,” said Thompson. “But the key thing in these reports that stood out to me was a statement saying, ‘You can’t miss this diagnosis, because if you remove the tumor and it is truly pumping out FGF23, you can cure these patients.’

“I went into David’s room, and we talked about it, and I said, ‘If you asked 99 neurosurgeons what this is, they would tell you it’s a meningioma, and that’s kind of what I think it could be too. But, if it really is the culprit, we should surgically remove it, because it could cure you.”

Unbeknownst to Dahir and Thompson, Covington’s wife, Natalie, who is earning a PhD as a researcher, had brought a manila folder filled with PubMed articles about TIO to both appointments, prior to the potential diagnosis ever being raised.

Natalie Covington, a PhD candidate in Hearing and Speech Sciences, was determined to find the cause of her husband, David’s, debilitating bone fractures. Photo by Joe Howell.

“My wife had read all about tumor-induced osteomalacia even before we received the diagnosis. She brought 11 case studies to my appointment with Dr. Thompson. She somehow found it online,” said Covington. “Talk about being fortunate — if anyone else was my wife, the outcome could have been completely different.”

“Natalie was tenacious about this. She had studied and researched it, and she was going to figure this out. She was determined to get David the right care. Her determination struck me from the beginning,” said Thompson.

Covington agreed to the surgery, and on July 12, 2018, his tumor was removed. The results of his pathology required a week of waiting, but Covington began feeling better immediately. His FGF23 levels dropped back to normal, and everything else normalized with it. He was released to Vanderbilt Stallworth Rehabilitation Hospital five days later, where he spent three weeks recovering before continuing outpatient treatment at the Vanderbilt Dayani Center.

“By the time I left Stallworth, I was able to climb a flight of stairs, which was great, because we live on the second floor of our building without an elevator. My first week at Stallworth, I remember being told we should consider moving,” said Covington.

By September, he was back to teaching, and a month later, he finished physical therapy altogether.

“My body was just ready to go — it wanted to be well,” said Covington. “I started running this summer, which I had never done before. My wife and I have gone to some swing dances. It felt good to feel like I could be an active participant in my own classroom again.”

“In six months, David went from walker, to cane, to nothing, to square dancing. He is healing his osteomalacia and has corrected all of his metabolic abnormalities due to low phosphorous levels. It has been so rewarding to see someone get better so quickly,” said Dahir, noting that many cases of TIO likely go undiagnosed for far longer than two years. Serum phosphorous levels are not often checked on a comprehensive metabolic profile, making the condition easy to miss for anyone who has never seen it before.

“I think we all got lucky because David and Natalie both pressed for a diagnosis and did their research. They have been such active participants in David’s care. It doesn’t get more patient-centered than that,” said Dahir. “I am so grateful to have been a part of David and Natalie’s journey.”


A humbling experience

For Thompson, the takeaways from Covington’s case go far beyond a lesson in TIO.

Reid Thompson, MD. Photo by Joe Howell.

“This experience was humbling for me. Can you imagine me walking into David’s room and saying, ‘I’m an expert, and you have a meningioma?’ We can consider ourselves experts, but there are a lot of things we don’t know, and that’s the lesson I’ve tried to teach our residents,” said Thompson, who has been practicing medicine for 30 years.

“You have to take the time to get as much information as you can before you walk into a room, meet a patient and develop a plan, especially if it’s going to involve an operation. You need to be humble enough to say, ‘I’ve never heard of TIO. I better learn something about it.’ You have to continually re-educate yourself. That’s medicine. And if you do that, good things can happen.”

Covington’s latest scans in March 2019 showed his bone density level has returned to normal, and his fractures have healed. He has a one-year follow-up scheduled for August, and his brain will continue to be monitored for changes out of caution.

He feels lucky to have been in the right place at the right time.

“I was pretty bummed when we had to move to Nashville, but then being here turned out to be exactly where I needed to be — in a city where there’s a hospital with Dr. Dahir and Dr. Thompson,” said Covington. “Both of them were so friendly, and we were impressed with the quick diagnosis. They really blew us away. I’m so grateful.” n