Metatarsal Bone Fractures and a Rare Bone Disease Hiding in Plain Site

11/23/22 • 12 min

A patient in her mid-50s complains of foot and leg pain. She's post-menopausal with low bone density. A classic case of post-menopausal osteoporosis.

Not exactly.

And it won’t start to become clear until it gets to the point of her having repeated metatarsal bone fractures.

Let’s go back a little. It’s 2005. Our patient visits her family doctor complaining of pain in her legs and feet. But the discomfort she's experiencing isn't your typical aches and pains associated with aging.

“She develops a lot of [foot and leg] pain ... So much so that she required pain management for this pain and her gate started to become affected,” shares Dr. Katherine Dahir, a professor of medicine at Vanderbilt University, who specializes in metabolic bone disease.

Her gait becomes wobbly and she’s experiencing an acceleration of degenerative changes in her spine. An osteoporosis screening reveals she has low bone density. She’s diagnosed with post-menopausal osteoporosis and is treated with bisphosphonates, the standard of care for patients with osteoporosis.

And this is when things get much more complicated.

Although all signs show an improvement in bone density, she begins to experience metatarsal bone fractures, which is highly unusual with osteoporosis. And not only does she have these unusual fractures, the fractures will not heal.

“And so that's when you need to put your thinking cap on and try and figure out, why is this patient a treatment failure?” says Dr. Dahir.

To solve the case, the patient’s team studies her labs and finds a missing flag. “... It was called alkaline phosphatase, which is seen in a routine chemistry panel. Back at that time, it was only flagged if it was above the normal reference range because that usually indicates liver disease, but it wasn't flagged if it was below the normal reference range because that was considered to be non-significant.”

But this finding would prove to be very significant. Combined with new research at the time, it helped identify a diagnosis for this patient — showing the importance of medical research that leads to more treatment options and more hope for patients.

A patient in her mid-50s complains of foot and leg pain. She's post-menopausal with low bone density. A classic case of post-menopausal osteoporosis.

Not exactly.

And it won’t start to become clear until it gets to the point of her having repeated metatarsal bone fractures.

And this is when things get much more complicated.

“And so that's when you need to put your thinking cap on and try and figure out, why is this patient a treatment failure?” says Dr. Dahir.

Previous Episode

Hypophosphatemia and the Secret Locked in a Child’s DNA

A toddler is taken to his pediatrician because his parents are concerned he might be small for his age. The pediatrician diagnoses him with knock knees, but there’s no cause for alarm.

Although the child doesn't have any other known medical conditions, something is happening in secret, inside his DNA that won’t be discovered until a diagnosis of hypophosphatemia is discovered some time later. And if this disease is ignored, it can quickly become deadly.

But back to that first appointment. “At that time, he had a rather normal diet, was taking [multivitamins] so his intake of vitamin D was at the recommended daily allowance,” shares Dr. Michael Levine, a pediatric endocrinologist at the Children's Hospital of Philadelphia. “And because he had no other medical disorders and no other conditions that were of concern, his pediatrician decided that they would just watch him to see whether he could outgrow his knock knees, and whether this might improve his overall growth.”

At the age of 7, there is little to no progress. He visits an endocrinologist. Nothing significant is found. At 10, an orthopedic surgeon operates on the child’s knock knees.

Two years later, he visits Dr. Levine for the first time. “When we first saw him, we were impressed by his prior history of knock knees, which had its onset in his toddler years, and we looked carefully at the evaluation that his pediatric endocrinologist had performed some years prior that disclosed normal levels of serum calcium, normal levels of PTH, normal alkaline phosphatase, and a normal serum 25-hydroxy vitamin D, which in the mind of the first pediatric endocrinologist had effectively ruled out rickets or osteomalacia.”

But one test hadn’t been done — a test for serum phosphorus level, and when the results come back showing hypophosphatemia, this becomes a key to the child’s diagnosis.

“When you have a child that doesn't respond as you might expect to calcium and vitamin D,” advises Dr. Levine, “you have to take that next step and begin to ask, could this be due to a genetic defect in the vitamin D system, or could it be a genetic defect in phosphate metabolism?”

As it turned out, the child’s disease was genetic, and this unlocked the path to treatment. And while everything worked out in the end, it’s hard not to think about how this story could have been very different had one simple test been run, or if genetics had been considered sooner.

Next Episode

A Lump on the Skull and the Misdiagnosis of a Rare Bone Disease

In 1964, Nancy, a 5-year-old, is having her evening bath when her parents discover she has a lump on the skull the size of a grapefruit. This would mark the onset of a mysterious and debilitating disease that researchers are still struggling to understand.

Over the next 40 days, medical professionals struggled to discover what was causing the lump on the skull. Each test seemed to exacerbate the swelling in Nancy's neck. In hindsight, that was a big clue, but it took doctors a while to recognize it.

Instead, what happened next was a common mistake when it comes to patients with this disease. Nancy was diagnosed with terminal cancer. Doctors said she had less than a year.

Yet, over the next few months, Nancy's condition didn't progress. She actually seemed to get better. Over the next few months, she was taken to a series of specialists. It was finally an oncologist who noticed something that was pivotal to her diagnosis ... her toes. Misshapen big toes — generally short and bending inward — are a hallmark of Nancy's disease.

While Nancy had several telltale signs of the disease, diagnosing rare diseases is difficult in part because they’re exactly that: rare.

“I can see how a practicing physician may feel a rare disease, ‘I'm never going to see it.’ But [this disease] is so striking that I think once you see someone with the disease ... the image stays in your mind and even if someone, as a general internist or a pediatrician, never expects to see the case, you never know,” shares Dr. Eileen Shore, a medical researcher and geneticist specializing in musculoskeletal disorders at the University of Pennsylvania School of Medicine.

And early diagnosis of this — and other rare diseases — is crucial, not only for treatment but to avoid diagnostic tests that can harm patients. While Nancy did finally receive a definitive diagnosis, many of the earlier diagnostic tests were actually causing more harm than good.

“If you just have that in the back of your mind, that you have a vague image of what [it] is and see a patient who you think might have it,” says Dr. Shore, “to send a referral and get it confirmed, just think of the difference it would make in that family's life.”