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.
There’s no cure for this chronic, progressive disorder. The goal of treatment is to reduce symptoms.
Continue reading to learn more about FOP and why early diagnosis is crucial, plus tips for raising awareness of this condition.
|What is Fibrodysplasia Ossificans Progressiva (Stoneman Syndrome)?|
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.
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 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.
A person with FOP can eventually become completely immobilized.
FOP does not cause extra bone growth to the:
- extraocular muscles
- cardiac muscle
- smooth muscle
FOP is caused by a 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, it’s a new mutation in a person with no family history of the disease.
A parent with FOP has a
FOP is extremely rare. There are 800 confirmed cases worldwide, with 285 of them in the United States. Gender, ethnicity, and race play no role. Unless you have a parent with FOP, there’s no way to assess your risk of developing the condition.
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
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.
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 your 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.