FD/MAS 101

FAQs about Fibrous Dysplasia and McCune-Albright Syndrome (FD/MAS)

What is Fibrous Dysplasia/McCune-Albright Syndrome?

The name of this condition, Fibrous Dysplasia/McCune-Albright syndrome (FD/MAS), can sometimes be confusing. Some people only have affected bones, in which case it might be called FD. When bones and other tissues are affected, it is called MAS. Since both FD and MAS are caused by the exact same gene mutation, and since many people with FD also have other tissues involved, the FD/MAS Alliance and doctors have decided to call it FD/MAS. It is a rare condition caused by a mutation in the gene GNAS. The mutated gene produces a protein, Gs alpha, that is dysfunctional. Gs alpha is a sort of “on/off” switch in cells, and the mutated protein is stuck in the “on” position. Depending on the cell or tissue affected, the “on” switch has a different effect.

The tissue most commonly involved is the bone (FD). Here the mutated protein makes it, so bone cells aren’t able to mature into normal bone. When endocrine organs, such as the thyroid or ovary, are affected, the effect of the “on” switch is to make excess hormones. In certain skin cells, it produces pigment, leading to darkened skin, sometimes called café-au-lait macules. Since the Gs alpha protein is produced in almost every cell in the body, many organs can be involved.

Individuals may have one or many features of the condition, which can occur in any combination. There is no cure for FD/MAS. However, medications or surgery can usually alleviate symptoms.

What is Fibrous Dysplasia?

Fibrous dysplasia (FD) is a condition that arises from abnormal bone cells that produce weak bones that are prone to fractures and/or bending The type and severity of the complications depend on where in the skeleton the FD is located and how much FD is in that location.

FD varies among individuals. If a single bone is affected, it is called monostotic FD, and if multiple areas are affected, it is termed polyostotic FD. Most complications result from fracture(s), deformity, functional impairment, and/or pain.

What are the symptoms of Fibrous Dysplasia and McCune-Albright Syndrome (FD/MAS)?

Some people with FD/MAS may have no symptoms; the bone lesions may be found only because an X-ray was done for some other reason. Others, especially those with more bones involved, may have many symptoms, including pain, enlargement or deformity of the bone, and fractures due to the weakened bone. Symptoms may include bone pain and deformity, a waddling walk, and/or scoliosis (curvature of the spine).

Those who have MAS may have various endocrine problems such as early puberty or over-production of thyroid hormones, growth hormone excess, Cushing’s disease (excess cortisol), and/or low blood phosphate.

The skin may have areas of increased skin pigment, often called café-au-lait macules. The term “café-au-lait,” however, refers to the color of the lesions in light-skinned individuals, which resembles the color of coffee with milk. In dark-skinned individuals, the lesions may be more challenging to see. The pigment distribution pattern is distinctive, often starting or ending abruptly at the midline of the body. The borders tend to be jagged and irregular. The macules are usually present at birth and do not change significantly over a patient’s lifetime.

Is Fibrous Dysplasia/ McCune-Albright Syndrome (FD/MAS) hereditary?

FD/MAS is not hereditary. We did not get FD/MAS from our parents, and we cannot pass it on to our children. FD/MAS is caused by a mutation during a baby’s development while still in the uterus. FD/MAS is a genetic disease because the mutation happens before birth. If the mutation occurs early in development, many tissues may be affected. If it occurs late in development, fewer tissues may be affected.

Why did I get Fibrous Dysplasia/ McCune-Albright Syndrome (FD/MAS)?

We do not know why the FD/MAS mutation occurs. The gene involved in FD/MAS seems to be especially susceptible to mutations. Although FD/MAS is rare, it occurs in males and females and people of all races and all parts of the world. It is likely that the mutation occurs randomly. There is nothing that a parent did that caused or the FD/MAS mutation to occur.

The doctor called my Fibrous Dysplasia a tumor. Do I have cancer, and can it become malignant?

FD is not cancer. “Tumor” simply means abnormal growth. Tumors can be malignant (cancerous) or benign (non-cancerous). Many people prefer to use the term “lesion,” generally meaning any defect, and avoid confusion with malignant bone tumors. An FD bone lesion can become cancerous, but this is rare, occurring in less than 1% of FD cases.

How is Fibrous Dysplasia/ McCune-Albright Syndrome (FD/MAS) going to affect my life now and in the future?

There is no simple answer to this question. The effects of FD/MAS are as different as each person who has it. For some people, it has no impact at all, while others may end up needing a cane or a wheelchair. The vast majority of people with FD/MAS lead full, meaningful lives. In rare cases, there can be loss of vision. In some cases, there is a partial hearing loss that can be normalized with hearing aids. An important feature of FD/MAS is that almost all of the tissues that will be affected are affected by an early age – in most cases before 10. So that if a thorough evaluation is done, it can be determined what tissues are affected, and just as importantly, what tissues are not and almost certainly will not be affected. Once the affected tissues are determined, it becomes easier to monitor them over time.

How rare is Fibrous Dysplasia/McCune Albright Syndrome?

It is difficult to know how many people might have the disease. Many will never know it because they don’t experience the complications that lead to a diagnosis.

What types of doctors or specialists are best suited for working with me on this disease?

Because bone is the most commonly involved tissue, most people will need an orthopedic surgeon. If bones in the skull are involved, an ear, nose, and throat (ENT) doctor may be needed. If endocrine organs are involved, an endocrinologist may be needed. Depending on the severity of the condition, a team of medical professionals and service providers may be needed. If this is the case, it is often best to try and get one doctor function as the team leader and make sure communication between the doctors is adequate.

At what point should doctors or specialists be consulted?

It is probably best to see specialists shortly after diagnosis to understand what aspects of the disease are present and which are not. Try and get a sense of your doctor’s experience with FD/MAS or other rare disorders. If he or she is inexperienced (or even if he or she isn’t), it’s often useful to get second opinions – especially if a procedure, operation, or medication is being recommended. Read more.

What research is being conducted for Fibrous Dysplasia/McCune-Albright Syndrome?

The most active centers doing research in FD/MAS are the National Institutes of Health (Bethesda, Maryland), INSERM (Lyon, France), Institut National de la Santé et de la Recherche Médicale (Montpellier, France), Leiden University Medical Center in the Netherlands, and Oxford University (Oxford, England). There is an excellent, cooperative network of doctors around the world that care for FD/MAS patients who are eager to communicate with your doctor if he or she is willing to reach out for help and guidance.

What tests are most commonly performed for Fibrous Dysplasia/McCune-Albright Syndrome?

A total body nuclear medicine bone scan is the best test for getting a picture of what areas of the skeleton are involved with FD/MAS. X-rays are often the best for viewing disease in long bones (legs, arms, etc.). A CT scan is the best way to assess FD/MAS in the skull. Ultrasound tests of the thyroid, testicles, uterus, and ovaries can sometimes be useful.

Blood tests that measure phosphorus, and thyroid hormones, etc. are critical. Read more.

It is essential to have vision (including visual fields) assessed by a neuro-ophthalmologist. An assessment of hearing is also useful. You can also reference the recommended treatment guidelines here.

Does FD/ MAS cause problems in pregnancy? Are there special precautions to take?

Most women with FD/MAS who want to have children are able to do so, and most pregnancies progress normally to normal deliveries. There is no evidence that pregnancy will make FD/MAS worse or increase bone pain. Women who have FD/MAS involving the spine, ribs, or pelvis should consider seeing a high-risk obstetrician (maternal-fetal-medicine) during pregnancy.

Women who have a history of precocious puberty continue to have ovarian cysts in adulthood. This may lead to irregular and heavy bleeding. It may take these women longer to become pregnant. Consider seeing a fertility specialist if pregnancy is not achieved after 6-12 months of unprotected sex. For more information, please reference this research article on FD/MAS and fertility.

Can people with FD/MAS participate in physical activities, including contact sports, or should they avoid them?

Patients with a lot of FD with a high risk for fractures should likely avoid contact sports and other high-risk activities. They should consult their medical professional.

Does craniofacial FD pose risks for the brain?

Craniofacial FD almost never disrupts the skull’s vital structures, including the vessels, brain, or nerves. Rarely, vision and hearing may be affected; however, persons with FD in the skull should have these checked regularly.

How can people with FD/MAS treat and manage pain?

When a patient with FD/MAS develops pain, the first step is to make sure it is not something that needs surgical treatment, such as fractures, bone cysts, and gait problems. Patients should also have their blood phosphate level checked, as this can worsen bone pain. For pain that is not related to these factors, the first steps in treatment should be conservative measures, including rest, massage, heat or cold packs, and over-the-counter medications such as ibuprofen and acetaminophen. For moderate or severe pain that does not respond to these treatments, intravenous medications called bisphosphonates (i.e., zoledronate and pamidronate) may help. These medicines should be given at the lowest dose and frequency needed to control the pain. Because FD is a chronic condition, long-term narcotic medications should be avoided if possible. If these medications are required, a specialist should prescribe it as part of a multidisciplinary pain plan.

How can people with FD/MAS slow the growth of bone lesions?

There are no treatments that can slow the growth of the bone lesions in FD/MAS. Bisphosphonates may help bone pain; however, there is no evidence that they affect the bone lesions, and there are serious side effects that should be taken into account. Uncontrolled growth hormone excess increases craniofacial FD growth, so screening and treating patients for this is critical.