Fibrodysplasia ossificans progressiva FOP: A rare disease but dramatic genetic disorder that turns muscles, tendons and ligaments into bone.

Medical Definition of Fibrodysplasia ossificans progressiva (FOP) Disease

Fibrodysplasia ossificans progressiva (FOP) is a condition in which bone grows outside the skeleton. Abnormal bone growth replaces connective tissue, including tendons and ligaments.

FOP is caused by a genetic mutation. It’s the only recognized condition that causes one organ system to morph into another.

The average age at the onset of misplaced bone formation is 5 years (range: from birth to 25 years). The most common starting sites are the neck, spine, and shoulder girdle. Some restriction of movement is present in most (80%) cases by age 7 years. By the age of 15 years, more than 95% of the patients have severely restricted the mobility of the arms.

Although progressive, Fibrodysplasia ossificans progressiva FOP is not cancerous.

Inheritance of FOP is genetically a dominant trait. However, sporadic (with no known family history) cases occur and are due to new mutations.

There’s no cure for this chronic, progressive disorder. The goal of treatment is to reduce symptoms.

What are the symptoms of  Fibrodysplasia ossificans progressiva FOP?

FOP becomes apparent early in childhood. Infants are usually born with short, malformed big toes. Bone and joint problems make it hard for babies to learn to crawl. About half of people with FOP also have malformed thumbs.

FOP is characterized by physical handicap due to bone forming in the wrong places and malformed big toes which often contain only one bone. Other features of FOP can include short thumbs, fifth finger clinodactyly (pinkie curved toward the thumb), malformed cervical (neck) vertebrae, the short broad neck of the femur (thighbone), deafness, scalp baldness, and mild mental retardation.

Bone overgrowth tends to start in the neck and shoulders, causing periodic bouts of painful inflammation. This is sometimes accompanied by a low-grade fever.

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 FOP may appear:

  • Movement can become severely restricted as the 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.
  • A person with FOP can eventually become completely immobilized.
Fibrodysplasia ossificans progressiva FOP does not cause extra bone growth to the:
  • tongue
  • diaphragm
  • extraocular muscles
  • cardiac muscle
  • smooth muscle

WHAT ARE THE CAUSES Fibrodysplasia ossificans progressiva FOP?

FOP is caused by a mutation in the ACVR1 gene. This gene is involved in the 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 the FOP, it’s a new mutation in a person with no family history of the disease.

A parent with FOP has a 50 percent chance of passing it on to their child.

Who gets Fibrodysplasia ossificans progressiva FOP?

FOP is extremely rare. There are 800 confirmed cases worldwide, with 285 of them in the United States. Gender, ethnicity, and race played no role. Unless you have a parent with FOP, there’s no way to assess your risk of developing the condition.

How is Fibrodysplasia ossificans progressiva FOP diagnosed?

Because it’s so rare, most doctors have never seen a case of FOP.

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 immunizations
  • difficulty moving
  • frequent injury due to falling
The 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.

The misdiagnosis rate could be as high as 80 percent. The most common misdiagnoses are cancer, aggressive juvenile fibromatosis, and fibrous dysplasia.

Early on, the symptom that can distinguish FOP from these other conditions is a malformed big toe.

It’s vitally important to get the correct diagnosis as soon as possible. That’s because certain tests and treatments for other conditions can cause flare-ups and encourage bone growth.

What is the treatment for Fibrodysplasia ossificans progressiva FOP?

There’s no treatment that can slow or stop disease progression. But treatment for specific symptoms can improve quality of life. Some of these are:

  • corticosteroids to reduce pain and swelling during flare-ups
  • nonsteroidal anti-inflammatory drugs (NSAIDs) between flare-ups
  • assistive devices such as braces or special shoes to help with walking
  • occupational therapy
There’s nothing that can make the new bones go away. Surgery would result in more bone growth.

An important part of PATIENT 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.

Prognosis of FOP

The prognosis for fibrodysplasia ossificans progressiva is poor because of the involvement of thoracic muscles and restrictive lung disease. Most fibrodysplasia ossificans progressiva patients are bedridden by the time they are in their 30s, and they usually die before they reach age 40 years.

Get Involved Raise Awareness Of  Fibrodysplasia ossificans progressiva FOP Disease

Some of the organizations that raise awareness for rare diseases in general are:

  • National Organization for Rare Disorders (NORD)
  • Rare Action Network (RAN)
  • Rare Disease Foundation
  • International Fibrodysplasia Ossificans Progressiva Association (IFOPA)
  • Canadian FOP Network
  • FOP Friends (U.K.)
One of the best ways to bring attention to a rare disease is to share your own story. Learn all you can about FOP so you can provide accurate information and answer questions.

So, how do you get the word out? Here are a few ideas to get you started:

  • Network with others affected by FOP or other rare diseases.
  • Contact organizations involved in FOP or rare diseases. Offer to share your story and volunteer to help.
  • Reach out to newspapers and television stations and offer to be interviewed.
  • Contact health bloggers and ask them to write about FOP or let you provide a guest post. Or start your own blog.
  • Offer to speak at schools and to local groups. Participate in health fairs. 
  • Contact state and national representatives to discuss research funding.
  • Use social media platforms such as Facebook, Twitter, and Instagram to spread the word.
  • Hold a fundraiser for an organization or a specific research project.
  • Get involved in Rare Disease Day.

Related Readings

Credit Source
    • Fibrodysplasia ossificans progressiva. (2017)
    • Fibrodysplasia ossificans progressiva (2017, January 24)

Email this page

Your privacy is important to 
Avatar Of Isreal Olabanji Dst Rn

Am Isreal olabanji a dental assistant and public health professionals and has years of experience in assisting the dentist with all sorts of dental issues. We regularly post timely and trustworthy medical information and news. My goal is to enlighten everyone in all aspects of health towards participating in fitness, Dental care, healthy recipes, child health, obstetrics, and more.

Leave A Reply