The skeletal system is a very important part of the body. The bones and muscles provide strength, support, movement, blood cell production, and calcium storage that all vital for survival.
When a disorder affects the bones in the body, it may lead to debilitating effects. Fibrous Dysplasia is a rare bone disorder. In this condition, the bone is replaced by an abnormal scar-like or fibrous connective tissue. As a result, the bones become weak and prone to fracture.
The disease may either affect just one bone or can be widespread – monostotic disease and polyostotic disease. Any bone can have this disorder, but the most frequently affected ones are the long bones of the legs, the ribs and the bones of the skull and face.
Fibrous dysplasia is not an inherited disease, unlike other bone disorders. Generally, it is caused by a gene mutation that is not passed from the parents to the child. However, there is still no cure for the disease, but the treatment options are geared toward repairing bone damage, stabilizing the bones and preventing bone deformities. Surgery is one of the commonly used treatment options for this rare bone disorder.
There are three main types of fibrous dysplasia including:
Monostotic fibrous dysplasia
This is the most common type of fibrous dysplasia that accounts for about 70 percent of all cases. This type of FD means involving just one bone, and it often occurs in the long bones of the body like the femur, ribs, and skull.
Polyostotic fibrous dysplasia
Another type of fibrous dysplasia is polyostotic which involves more than one bone. This type accounts for about 30 percent of all cases. The most commonly affected parts of the body are the bones in the head and neck.
This is a type of fibrous dysplasia that is linked to the hormone disturbances and skin pigment changes. This is a rare type of FD wherein just one in every ten is diagnosed. That’s about 3 percent of all cases.
Fibrous dysplasia can manifest numerous signs and symptoms including:
- Bone pain
- Bone fractures
- Bone deformities
- Lesions on the bones which may stop growing after puberty
- Walking difficulties
Signs and Symptoms in Children With FD on Skull And Face
- Facial asymmetry
- Nasal airway obstruction
- Problems with hearing and vision
- Jaw misalignment
- Difficulty in chewing or swallowing
- Shifting facial structure that can affect any bone on the face
Other Signs and Symptoms:
- Unusual gait
- Irregular bone growth
- Increased susceptibility to fractures
McCune-Albright Syndrome Symptoms:
People with polyostotic FD are at an increased risk of developing McCune-Albright Syndrome including:
- Onset of puberty before they reach ten years old
- Overactive pituitary gland
- Darkened spots on the skin called café-au-lait spots
The exact cause of fibrous dysplasia is still not fully understood, and the disease process is unclear. However, many researchers believe that fibrous dysplasia is caused by a mutation in the gene dubbed as GNAS1. Caused by a somatic mutation, which happens after fertilization, this type of rare genetic bone disorder is not inherited from the parents.
The mutation is just present only in some cells of the body, which means the effects may be confined to just one body part. This disease arises in an early cell division in the developing embryo and has no hereditary factors.
The scientists are not aware why these somatic mutations occur, but it makes the GNAS1 gene to become overactive.
Other theories on the cause of FD include:
- Abnormal activity in the bone forming tissues during pregnancy
- Localized infection or trauma
The most commonly affected bones in the body are the femur or thighbone, tibia or shinbone, humerus or the bone in the upper arm, skull, pelvis and the ribs.
Fibrous dysplasia is an uncommon disorder, and it’s diagnosed in children and adolescents. This disease is chronic and present throughout life. However, there are no known risk factors that might increase your chance of getting FD. It is not influenced by gender, race, geographic location, background and even environmental exposure.
In the long run, fibrous dysplasia may lead to complications such as:
- Bone fracture and deformity – The bone affected by the disease may become weak and cause the bone to bend. These weakened bones are prone to fractures even with no or little force.
- Arthritis – When the disease affects the joints in the body like those found in the pelvic bones and the legs, this may lead to arthritis.
- Cancer – In rare cases, the bone affected may form cancerous cells, leading to bone cancer.
- Problems with vision and hearing – The bones of the skull may become affected by FD, and the nerves on these bones that support vision and hearing may be affected too.
- Other complications – The other complications that might arise from FD include Cushing’s disease, heart rhythm problems, hyperthyroidism, rickets, and gigantism.
Early detection of the disease is important, especially among kids because once their skeletal system has matured, it may lead to permanent disability and bone deformity. However, if the disease is detected early on, there is a greater chance of preventing bone deformity and lesions to form. There is no cure for the disease, but early detection may lead to the prevention of further bone damage.
Since the affected part are the bones in the body, the most used tool to diagnose fibrous dysplasia is an X-ray. The radiologic test may show a distinct appearance described as “ground glass.” In some cases, the people who do not know they have the disease were diagnosed incidentally because of their X-ray result.,
This test may also show the doctor how much of the bone is affected and if the disease has caused a deformity in the bone. The doctor may also conduct a complete physical examination and medical history to determine the severity of the disease and presence of the symptoms.
There are other tests that the doctor may recommend such as:
- Imaging Tests – There are imaging tests that the doctor may recommend like computerized tomography scan (CT-scan) and magnetic resonance imaging (MRI). These imaging tests could provide cross-sectional or 3-D images of the bone.
- Blood tests – The blood tests could provide a picture of the overall health of the person and if the blood cells are still at a normal level. The longest bone in the body, which is usually affected by FD, is where bone synthesis happens.
- Bone Scan – A type of nuclear imaging test, a bone scan will provide the doctor images of multiple fibrous dysplasia lesions. In this test, a small radioactive tracer is injected into the blood and absorbed by the damaged portions of the bone.
- Biopsy – Another test to confirm the diagnosis is through tissue biopsy wherein a tiny needle is inserted to remove tissue samples from the bone for microscopic analysis.
In mild cases of fibrous dysplasia, the patient may discover the disease incidentally after an X-ray or physical examination after a fracture. For these patients, the risk of complications and the presence of signs and symptoms may be low. The treatment of fibrous dysplasia depends on the symptoms present and the severity of the condition.
However, the treatment of this disease involves taking medications and for some, undergoing surgery.
In some cases, the doctor might prescribe medicines for osteoporosis to help prevent bone loss. Dubbed as bisphosphonates, these drugs decrease the activity of the cells that dissolve bone. In fact, these drugs have been seen to strengthen the bones affected by fibrous dysplasia. However, these medicines should be prescribed by a licensed doctor.
Surgery of fibrous dysplasia is indicated in the prevention or treatment of fibrous dysplasia fractures or deformities. Surgical treatment for fibrous dysplasia involves the removal of the affected bone, and it will be replaced by a bone graft from another part of the body. Moreover, metal plates, rods, and screws may also be used.
The surgical treatment may help correct a deformity, repair a fracture that doesn’t heal even after casting, prevent future fractures and correct a difference in the lengths of the limbs. Surgery may also relieve the pressure on a nerve, particularly when the lesion is found on the skull or face.
For people with mild fibrous dysplasia, the outlook or prognosis is better than those who suffer from severe bone deformities. For patients, long term follow-up is important to prevent deformity as a result of the disease.
Patients should undergo yearly X-ray tests and imaging tests, especially on the affected areas to see if the lesion is getting bigger or not. Moreover, because FD rarely goes into remission, it is important to monitor the progression of the disease from time to time. This is particularly beneficial to patients with still immature patients. Once they have matured skeletal systems, the disease is not likely to progress anymore.
The early detection and intervention for fibrous dysplasia are important to prevent deformity. The patients should also seek medical advice from an endocrinologist for metabolic and endocrine testing. This is to determine if there are any endocrine anomalies and to treat them immediately and efficiently.