One of the rarest diseases in the world—Fibrodysplasia ossificans progressiva (FOP)—will turn your body into a frozen statue.

While horrific, FOP is an astonishing disease. It transforms your muscles and tendons into hard bone, locking them in place, according to a 2011 study by the University of Pennsylvania.

Slowly and surely you grow a second skeleton, rendering your body immobile. It’s a disease that eventually will entomb you in bones.

What’s worse is that surgery will exacerbate the condition. In fact, any sort of injury causes new bones to be formed. Even dental work, stretching your muscles too hard, or a viral infection can calcify your joints.

Cartilage transformed into bone on a patient’s back (Robert Pignolo/Orphanet Journal of Rare Diseases)

Luckily, the disease is not widespread—only one in two million people suffer from FOP. As far as worrying if you’ll develop this terrifying disease randomly? It’s impossible if you’re already an adult.

The disease is caused by a gene mutation, meaning you’re born with it. Usually, babies who inherit the gene show signs at birth–Their toes are deformed. Spontaneous bone growth erupts during childhood.

Malformed toes in FOP patient (Robert Pignolo/Orphanet Journal of Rare Diseases)

By the time patients reach the end of their 20s, they are bound to life in a wheelchair. Most don’t survive past the age of 40.

In a 2013 Reddit AMA session, 20-year-old Joseph Suchanek (or Reddit user Iguanajoe17), a FOP patient, described the first time he knew something was wrong with his body:

Joseph Suchanek as a child (Joseph Suchanek)

So far, a definite cure for the disease has not been found. But the future looks promising. In a 2015 study, researchers stopped the progression of the disease in mice.

In fact, one of the University of Pennsylvania grad students who is working on a cure for the disease, Michael Convente (or Reddit user MRC1986), unexpectedly showed up in a post about FOP in the Today I Learned community.

He explains the research:

And Convente’s team is not the only one researching the disease.

Get this—we might be able to understand the disease better by studying sharks. According to a 2015 study published in PLOS One, researchers discovered that elephant shark necks naturally fuse together, in a similar way to FOP.

While this is all fascinating, the disease is a very real horror that some people have to live with. One Reddit user sought donations for research to help those who suffer from FOP: