Last week a Dutch hospital announced that it had removed the entire top of a woman’s skull and replaced it with a plastic implant, custom-made using a 3-D printer. The story, with a video (below) and amazing photos of the 22-year-old woman’s delicate pink brain encased in a thin piece of clear plastic, went viral immediately.
But what I wanted to know, and couldn’t find in any of the reports, was what condition could make a person’s skull grow 5 centimeters (2 inches) thick, which made the surgery necessary.
There are several bone-thickening diseases that were possible contenders, sparking some initial speculation among science writers on Twitter: Could it be melorheostosis? Osteopetrosis, fibrous dysplasia?
But this one would be a stumper for anyone but Dr. Gregory House, or a Dutch geneticist. So I asked the hospital where the surgery was performed, UMC Utrecht in the Netherlands, and learned that the woman has van Buchem disease, a rare condition found almost entirely among small pockets of closely related Dutch people. The disease, formally called hyperstosis coricalis generalisata, was first described in 1955 by Dutch physician Frans van Buchem. Patients had thickened skulls and jaws, giving them a distinctive appearance, as well as thicker ribs and long bones. It was soon clear that the condition was passed down in families. Thirteen more cases turned up in the 1960s and ’70s, all in people living in a small Dutch village. In 2013, researchers were able to find 18 Dutch people with the condition.The thickening of the skull and jaw can be extreme. “The weight of the skull and mandible is grossly increased, in some patients to more than three times the normal weight,” researchers reported in 1998. People with the condition rarely break bones, including one case in which a patient emerged fracture-free after crashing a motorcycle into a tree at “very high speed.” The condition also makes it hard to stay afloat in water, so patients report having to swim continuously to avoid sinking.
We now know that van Buchem disease is caused by a genetic mutation on chromosome 17, and it’s an autosomal recessive trait, meaning that both parents have to have the mutation for their child to have the disease. That also explains why the disease has largely been confined to small pockets of the Dutch population where inbreeding is common. (Note that the recent surgical patient’s name and info has not been released, so we don’t know her family history.)
Why the Dutch? It may just be because this particular mutation happened randomly in someone in the Netherlands who was part of a small population. That person’s descendants would carry a copy of the mutated gene, and if later generations intermarried, two carriers could have children with the two copies of the gene needed to have the disease.
Van Buchem disease is similar to some other bone-thickening diseases, such as sclerosteosis, found mostly among Afrikaners in South Africa (another Dutch connection). Both conditions lead the body to produce lower- than-normal amounts of a protein called sclerostin. Bones don’t just grow once when you’re young and drinking your milk; competing bone cells are constantly building bone and breaking it down. Sclerostin helps bones maintain a balance, and without it they gradually build and build. And that’s how you end up with a 2-inch-thick skull.
The patient who received the new plastic skull had slowly lost her vision as her skull thickened and pressed in on her brain. She started to suffer from motor impairment, surgeon Bon Verweij reported. “It was only a matter of time before other essential brain functions would have been impaired and she would have died.”
The hospital waited three months after the surgery to report its results. The good news, Verweij says: “The patient has fully regained her vision, she has no more complaints, she’s gone back to work and there are almost no traces that she had any surgery at all.”
Surgeons implanted a plastic skull in a young woman’s head to treat van Buchem disease, a rare bone-thickening condition. (Note: video contains graphic images of an exposed brain.) Credit: UMC Utrecht
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