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Rare Disorder Turns People’s Bodies to Bones
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Her Muscles and Ligaments are Turning to Bone
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The Girl Whose Muscles are Turning to Bone
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What is Fibrodysplasia ossificans progressiva (FOP)?

Fibrodysplasia ossificans progressiva (FOP), is a rare autosomal dominant condition where the body’s soft tissues — muscles, ligaments, and tendons — turn into bone and form a second skeleton outside the normal one. FOP is the most disabling condition of ectopic skeletogenesis.

Progressive bone formation (ossification) causes loss of mobility as the joints become affected. Inability to fully open the mouth may cause difficulty in speaking and eating. Over time, people with this disorder may experience malnutrition due to their eating problems. They may also have breathing difficulties as a result of extra bone formation around the rib cage that restricts expansion of the lungs.

FOP often starts in early childhood. It begins around the shoulders and neck, then works its way down through the rest of the body. As the patient gets older, bone replaces more and more of soft tissue, but how quickly that happens varies from person to person. Any trauma to the muscle which results in inflammation of the muscle triggers rapid ossification in these patients.

Occurrence is extremely rare i.e 1 in 2 million. Only several hundred cases have been reported worldwide.

FOP is caused due to a genetic mutation in the ACVR1 gene. This gene is involved in growth and development of bones. The mutation allows them to grow unchecked. The gene can be inherited from one parent, but in most cases of FOP there could be a new mutation in a person with no family history of the disease.

It is an autosomal dominant disorder which means a parent with FOP has a 50 percent chance of passing it on to their child.

The disease progresses at a different rate for each person. Eventually, it affects the trunk, back, hips, and limbs. As the disease progresses, the following symptoms may appear:
  • Movement can become severely restricted as bone grows into joints.
  • The spine can become deformed or fused.
  • Limited mobility may cause balance and coordination problems that can lead to injury
  • due to falling. Even a minor injury can cause more inflammation and bone growth.
  • Bone growth in the chest can restrict breathing, increasing the risk of respiratory
  • infection. Any viral illness can trigger a flare-up.
  • Limited movement of the jaw can make it hard to eat, which can lead to malnutrition
  • and weight loss. Talking can also be difficult.
  • About half of people with FOP experience hearing impairment.
  • Poor blood flow can lead to pooling of the blood in the arms or legs, causing visible
  • swelling
As FOP is rare, most doctors have never seen a case of FOP. The most common misdiagnoses are cancer, aggressive juvenile fibromatosis and fibrous dysplasia. Diagnosis depends on medical history and clinical examination. Symptoms of FOP include:
  • malformations of the big toe
  • spontaneous flare-ups of inflammation or soft tissue swelling
  • increased flare-ups after injury, viral illness, or immunisations
  • difficulty moving
  • frequent injury due to falling
The earliest symptom that can distinguish FOP from these other conditions is a malformed big toe. Excess bone formation may be seen on imaging tests such as X-ray and MRI, but are not needed for diagnosis. The diagnosis can be confirmed with genetic testing.

There is currently no treatment that can slow or stop disease progression. FOP is chronic and there is no cure. Treatment can help ease symptoms and improve quality of life. Some of these are:

  • corticosteroids to reduce pain and swelling during flare-ups
  • non-steroidal anti-inflammatory drugs (NSAIDs) between flare-ups
  • assistive devices such as braces or special shoes to help with walking
  • occupational therapy

There is nothing that can make the new bones go away. Surgery would result in more bone growth. An important part of the treatment plan has to do with what to avoid. A biopsy, for example, can cause rapid bone growth to the area. Intramuscular injections, such as most immunizations, can also cause problems. Dental work must be performed with great caution, avoiding injections and stretching of the jaw. Blunt trauma or injury due to falling can cause a flare-up. Any physical activities that increase these risks should be avoided.

FOP can be dangerous during pregnancy, which can increase the chances of flare-ups and complications for both mother and baby.

The rate of progression is different for each patient and is difficult to predict. Some people go months or even years without a flare-up.

FOP can become severely disabling. Most people with FOP will need a wheelchair by the time they reach their late 20s. The median lifespan for people with FOP is 40 years.

Some organisations which raise awareness for FOP are:

If there is a known case of FOP in the family, it is absolutely essential for closest relatives like siblings, uncles, aunts and cousins to test for carrier status.

If a woman with a carrier status is pregnant, prenatal test is essential to determine if the fetus has the disease mutation.