This medical condition turns muscle to bone

One of the scariest medical conditions in the world, fibrodysplasia ossificans progressiva, changes muscle and connective tissue into bone. Over the course of a few decades, it turns the entire body into one huge skeleton.

There are a lot of frightening medical conditions out there, but one of the most terrifying has to be fibrodysplasia ossificans progressiva. Often starting in childhood, this condition turns muscles and tendons into bone, freezing a person over time. Recently scientists have figured out exactly what causes it, and a few treatments have been explored, but there is no known cure.

It starts with a mutation on the ACVR1 gene, which is the blueprint for a specific protein. It's one of the proteins that control the change of cartilage and muscle tissue into bone. This happens naturally, and in a limited way, as a baby grows to adulthood. Parts of the skeleton gradually harden until a person is full grown. In someone with fibrodysplasia ossificans progressiva that protein initiates the same process whenever a muscle or tendon is damaged. Whether it's overwork, bruising, or tearing, the tissue rebuilds as bone and freezes into place.

The process generally starts in the neck and shoulders, making a person unable to turn their head from side to side. As body parts are paralyzed and mobility declines, it's easier to cause damage to the rest of the body. Even minor stretches can cause ossification. One fibrodysplasia ossificans progressiva patient describes going to bed feeling fine and waking up with body parts newly paralyzed. Eventually, damage around the mouth causes it to freeze into position, so eating becomes difficult. Damage around the rib cage ossifies the chest and prevents it from expanding, causing breathing problems.

Since almost any surgical treatment causes more damage, there are few options for fibrodysplasia ossificans progressiva patients. For some time, protein from sharks, which have cartilage instead of bone forming their skeletons, was studied. Today, protein kinase inhibitors, which inhibit the function an enzyme that helps proteins function, have stopped ossification in mice. Because the ACVR1 gene causes the condition, it's hoped that sometime in the future gene therapy might help. Right now, it looks like the only real treatment is extreme caution to prevent tissue damage.

[Via NCBI, Genetics Home Reference, NCBI]