FOP (Fibrodysplasia ossificans progressiva)

November 12, 2012

FOP (Fibrodysplasia ossificans progressiva)

This is a disorder where the ligaments and tendons are slowly replaced by bone which in turn forms bones outside the skeleton meaning that movement becomes constrained.

Early in childhood indications begin to appear starting at the shoulders and neck and moving downwards to the body and limbs.

Bones that form outside the skeleton (extra-skeletal) leads to mobility loss over a period of time as the joints are affected. Difficulty may be experienced in eating and speaking which is due to the patient not being able to open their mouth. Malnutrition may occur with this disorder as it becomes more difficult to eat. And as bone formation is growing around the rib cage breathing difficulties may be experienced.

Should a patient with fibrodysplasia ossificans suffer from a fall or have invasive surgery, myositis (inflammation) and swelling of muscles may occur and this is followed quickly by ossification in the area which has been injured. Flu and other viral illnesses may cause flare-ups to occur.

Patients who suffer from fibrodysplasia ossificans progressiva tend to be born with abnormal big toes. The abnormal big toes are a characteristic of this disorder. And this helps to differentiate between other muscle and bone problems. It may be patients who are affected with this disorder also have shorter thumbs and suffer from skeletal abnormalities.

Fibrodysplasia ossificans progressiva is disorder which is extremely rare. There have been a few hundred cases that have been reported, and worldwide there appears to be approximately one person out of two million who suffers from this disorder.

Changes in a gene called ACVR1 are related to the cause of FOP (fibrodysplasia ossificans progressive). This gene sends instructions to produce BMP (bone morphogenetic protein type 1 receptors) which belongs to the family of proteins. This ACVR1 protein can be found in a variety of tissues in the body including cartilage and skeletal muscle. This helps in controlling the development and growth of muscles and bones which includes slowly replacing the cartilage by ossification that happens in the normal maturation of the skeleton from birth into young adulthood.

Researchers who have studied this ACVR1 gene believe that a mutation occurs that changes the receptor shape when particular conditions occur and that the mechanisms controlling the activity of the receptor are disrupted. Because of this the receptor could be on constantly (constitutive activation). The constitutive activation of this receptor causes the bone and cartilage to become overgrown and fusion of joints occurs, which results in symptoms and signs of fibrodysplasia ossificans.

Cases of fibrodysplasia ossificans occur because of new changes and alterations in the ACVR1 gene. Cases can appear in people who have no family history of this disorder and in a few cases the patient may have inherited this disorder from a parent who has the dominant defective gene.

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