SciTech

HealthTalk: Fibrodysplasia ossificans progressiva

Most people are familiar with how human skeletons look; perhaps they have seen one hanging in a classroom or in a medical documentary. The skeleton is highly moveable, with many joints that allow humans to perform rigorous activities such as gymnastics. A normal adult skeleton has a total of 206 bones, which are attached to muscles by tendons or to other bones by ligaments. However, one disease, fibrodysplasia ossificans progressiva, or FOP, causes tendons, ligaments, and muscle to turn into bone, forming a second skeleton that looks like sheets of bone.

An initial sign of FOP is myositis, which is a term that means an inflammation of the muscles. They are sometimes referred to as “flare-ups,” and they anticipate the conversion of tissue into bone. These flare-ups appear as large red lumps, and they may be warm and painful. For FOP patients, myositis can occur due to muscle trauma, such as damage sustained from a fall, invasive medical procedures, and even viral illnesses, according to www.disabled-world.com.

The first growth of extra bone, for most patients, occurs in the neck, spine, and shoulders, and growth continues over their lifetime to other parts of the body. When extra bone forms in joints, it causes immobility of the affected joint. FOP can also deform the spine, causing scoliosis, and fuse the jaw. If bone covers the ribcage, breathing can become difficult because expansion of the ribcage is severely inhibited. Eventually, FOP patients will become bedridden, usually when they are in their 30s, because bone growth will cause almost complete immobility.

People with FOP are usually born with malformed big toes, although it is not understood why this happens. However, the major symptoms of FOP do not appear at birth, but rather they appear slowly over the first two decades of life, according to Discovery Health. Doctors must take caution when diagnosing such a disease, since the presence of malformed big toes does not necessarily indicate the presence of a rare disease.

FOP can be diagnosed through extensive studies, including genetic testing and X-rays, which may detect abnormal bone formation. However, according to www.ucsfbenioffchildrens.org, the rate of FOP misdiagnosis is around 80 percent. Misdiagnosis can result in biopsies and other invasive procedures that result in extra bone growth. FOP is commonly diagnosed as cancer, tumors, and other diseases that cause abnormal bone growth.

The prevalence of such a disease is one in 1.64 million people worldwide, according to www.medscape.com, and is more common in females than in males. Genetic studies have shown that it is a dominant mutation: Humans have two copies of a gene, which dictate a person’s growth and development. For a dominant mutation, one mutation of a specific gene is enough to cause FOP.

Currently, no known treatment for FOP exists, but a number of drugs can alleviate symptoms. However, caution is still taken because FOP symptoms differ greatly among individuals, and the drugs have a specific purpose. For example, muscles that are being ossified, or turned into bone, can spasm; muscle relaxants can be given to decrease the spasms, but this does not reverse the process of ossification. Because bone growth can occur as a result of trauma, surgery to remove bone is not an option, as this may induce the growth of extra bone at the site of surgery.

Over the past few years, researchers have been looking into a natural chemical produced in sharks as a treatment for FOP. The chemical, called squalamine, can be found in the livers of numerous shark species, and it was first used as an antibiotic. However, it also reduces blood vessel formation in the site of its application. Squalamine is currently being tested on FOP patients.

While not much is known about this tragic disease, research will lead to insight into bone development and the viable treatment of various bone disorders.