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Aaron Blocker’s bones had been giving him trouble for as long as he could remember.
Born with severely deformed legs, Blocker as a baby wore metal leg braces while he slept, allowing him to walk. However, he said, his legs “always hurt.” The rash of broken bones started when he was 10 and fell on his hand, breaking several fingers. A few years later, he broke his nose for the first time when it was clipped, but not hard, by a soft plastic swing.
“My family just thought I was a clumsy kid,” said Blocker, 30, who grew up near Jackson, Miss., where he still lives. “I was very active.”
Over the years, Blocker said, doctors set his broken bones and treated other orthopedic problems, including scoliosis, a sideways curvature of the spine. But no one offered to take a closer look, even after Blocker underwent multiple surgeries to replace both hips in his 20s, an operation normally performed on people decades older.
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The premature and unexpected failure of these hip replacements convinced Blocker that his skeletal problems had an overlooked cause. At age 24, while a biomedical research student, Blocker harnessed his skills and trained them on himself. He spent several weeks digging through his medical records and scouring scientific websites before hitting the dirt: a possible diagnosis that was later confirmed by genetic testing.
“It was a relief to have an answer,” said Blocker, who works for an insurance broker. “But I’ve always wondered how this was missed for so long?”
The answer, one of his doctors later theorized, may reflect evolving scientific knowledge of his rare diagnosis as well as Blocker’s own complicated medical history.
Blocker’s bones weren’t his only problem.
“I had a lot of trouble with my teeth growing in,” he said. His molars, usually the largest and strongest teeth, would inexplicably crack. By the time he graduated high school, he had seven teeth removed. Blocker also had multiple cavities, which his dentist attributed to “weak teeth.” He had two wisdom teeth removed in high school and healing was unusually slow; the oral surgeon noted a weakness in his jawbone but did not recommend further investigation.
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In his mid-teens, Blocker developed recurring problems with his right shoulder. The first time he sprained it while throwing a ball. Another dislocation occurred while he was sleeping, but no one could explain how or why this happened.
During his senior year in high school, Blocker was forced to grapple with a more pressing problem. After a two-week hospitalization that capped months of abdominal pain during which his weight dropped to 100 pounds, Blocker, who is 5-foot-10, was diagnosed with Crohn’s disease. Chronic inflammatory bowel disease causes severe diarrhea and weight loss.
He was prescribed prednisone, a major drug used to treat Crohn’s disease. Blocker said he took a relatively low dose of the corticosteroid, which reduces inflammation, for about eight weeks.
A year later, in January 2011, when the disease flared up, Blocker was again hospitalized and underwent a CT scan of his abdomen. The scan revealed an alarming and unexpected incidental finding: avascular necrosis of both hips. A bone density scan also found Blocker had severe osteoporosis.
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Avascular necrosis occurs when the blood supply to the bone is interrupted, causing collapse and death of the tissue and threatening the integrity of the structure. Causes include long-term steroid use, especially in high doses, excessive alcohol consumption, fractures, and various medical conditions. People with inflammatory bowel disease may have a reduced ability to absorb calcium and vitamin D, which can affect bone density and lead to osteoporosis, a condition in which bones become weak and brittle.
“The orthopedist told me my femurs were dying and said it might be related to the prednisone,” Blocker recalled. But this seemed doubtful: he had been taking the drug for about eight weeks, and not at a high dose.
A year later, after other treatments failed and Blocker’s hips began to collapse, both hips were replaced in surgeries three months apart.
“I spent 2012 mostly inside,” said Blocker, then a 20-year-old college student who took a year-long medical leave from Mississippi College and returned home. “It was very hard.”
Between 2012 and 2016, Blocker said, he again broke his nose and wrist, along with several toes. One evening in February 2016, Blocker was sitting on her bed when she turned to grab something from her nightstand. He instantly felt a searing pain in his thigh, so severe that he could not move. His wife, Emily, called a friend, who carefully pulled Blocker out of bed, carried him to the car and drove him to a nearby emergency room.
Nearly 100 doctors have tried to diagnose this man’s devastating disease – without success
Doctors diagnosed a partially dislocated hip. Blocker was sent home on crutches and told to see an orthopedist, who told him his new hips had disintegrated after less than four years.
“I knew in my gut that something was wrong,” he recalls. “It didn’t make sense to me that they failed when they should have lasted more than 15 years. I thought, ‘I’ll try to figure it out if nobody else does.'”
Blocker gathered his medical records from doctors’ offices and hospitals around Jackson and began digging.
Going back years, he noticed that his alkaline phosphatase (ALP) level, a component of a routine blood chemistry panel, had always been extremely low. ALP is an enzyme found primarily in the liver, bones, and digestive system. High levels of ALP can signal cancer, a liver problem, or mononucleosis. Low levels may indicate zinc deficiency, malnutrition, or a rare genetic condition called hypophosphatasia (HPP), which affects approximately 1 in 100,000 people and causes bone and tooth problems.
“I realized I fit every symptom,” Blocker said. “I had a moment that felt like clarity. I thought, “This could be it.” “
Hypophosphatasia is an inherited disease caused by mutations in the ALPL gene that disrupt mineralization, the main process by which calcium and phosphorus are deposited in developing teeth and bones, making them strong and hard. There are several forms of the disease that differ in age of onset. The most severe form manifests prenatally, and the mildest affects only the teeth.
The disease is particularly common among Mennonites in Manitoba, a province in Canada, where about 1 in 2,500 babies are born with severe HPP, which is inherited in an autosomal recessive fashion: Two copies of the mutated gene, usually one from each parent, are needed to causing disease. In such cases, the parents may be carriers who show no signs of disease. Less severe autosomal dominant forms of HPP result from inheriting a defective gene from one parent who may also have the disease.
Blocker took the articles he found to his family doctor, who had never heard of HPP. He referred Blocker to a geneticist at the University of Mississippi, whom he saw in July 2017.
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After reviewing Blocker’s medical history, including his clubfoot at birth, multiple fractures, osteoporosis and a history of hip replacements, the specialist ordered genetic testing for HPP.
The results confirmed Blocker’s hypothesis: He had the disease inherited in an autosomal dominant pattern. Blocker, who was raised by his maternal grandparents, said he doesn’t know which parent passed him the gene.
“I was relieved,” he said of the news that the cause was something other than clumsiness or bad luck. “It was nice to be right and not feel like a crazy person and have an answer.”
Connect with an expert
It quickly became clear to Blocker and his doctors that he would need specialized care out of state. The nearest expert, 400 miles north of Jackson, was endocrinologist Kathryn Dahir of Vanderbilt University School of Medicine in Nashville. A specialist in metabolic bone disorders, Dahir treats patients and families affected by HPP from cradle to grave.
Blocker saw Dahir in early 2018 and spent two days at Vanderbilt undergoing testing and evaluation at the Center for Bone Biology. He is among a handful of about 100 HPP patients treated by Dahir who have self-diagnosed their condition.
“Aaron is a really smart guy — really medically curious,” she said.
One reason his case may have escaped diagnosis, Dahir said, is that the milder form he suffered from — juvenile onset — was only recently described. “Our understanding of the disease has really evolved over the last decade,” she said.
And there may have been a clinical reason doctors didn’t follow up on Blocker’s unusually low ALP levels. Until very recently, low levels were not necessarily considered clinically significant unlike high levels and may not have been flagged. That has changed, she said, and “is just a quantum leap forward.”
Blocker’s history of Crohn’s disease may also have played a role. Although there is no known link between HPP and Crohn’s disease, “it makes the diagnosis more complicated,” notes Dahir. “It’s really hard to have two things that affect your musculoskeletal system. It’s hard to know what causes what.’
After competing with his health insurance company, Blocker was approved to take Strensiq, the only drug approved to treat HPP. Blocker said the drug, which he injects six times a week, costs his insurance company about $1.6 million a year. The drug is designed to replace alkaline phosphatase and improve bone…
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