What Is Facioscapulohumeral Muscular Dystrophy?

Facioscapulohumeral muscular dystrophy (FSHD) is the third most common type of muscular dystrophy. Although it also causes progressive muscle weakness, FSHD does not shorten your life expectancy as other forms of muscular dystrophy do.

Named after the primary body parts that it affects—the face, shoulders, and arms—FSHD usually begins in the teenage or early adulthood years and progresses very slowly.

This article will review the types of facioscapulohumeral muscular dystrophy that can develop, what to expect if you have this condition, and how it can be treated.

Types of Facioscapulohumeral Muscular Dystrophy

There are three forms of FSHD. Each type has the same symptoms and progression, but their genetic origins are different.

All forms of FSHD involve defects in chromosome 4, which makes different proteins in the body. The chromosome is usually made up of between 11 and 100 repeating pieces.

D4Z4, the portion of the chromosome that is affected by FSHD, usually has an abundance of methyl groups that play a vital role in the way DNA replicates. With all forms of FSHD, there is a shortage of these methyl groups, and several genes in your DNA become silenced or inactive.

Facioscapulohumeral Muscular Dystrophy 1 (FSHD1)

In FSHD1, the lack of methyl groups is caused by a shortening of the D4Z4 region of chromosome 4. In people with FSHD1, the D4Z4 region is made up of 1 to 10 repeating sections compared to the usual 11 to 100.

Specifically, FSHD1 develops as a result of a mutation in the DUX4 gene, which plays a role in the activity of other genes and muscle cells.

FSHD1 is the most common form of FSHD, affecting about 95% of the people with the disease.

Facioscapulohumeral Muscular Dystrophy 2 (FSHD2)

FSHD2 is clinically identical to FSHD1, but instead of having fewer methyl groups, chromosome 4 has a normal number of methyl group sections that are spread further apart. In this form of FSHD, a gene called SMCHD1 is affected instead of DUX4.

FSHD2 is the more rare form of FSHD, affecting only about 5% of people with the condition.

Early-onset (Infantile) Facioscapulohumeral Muscular Dystrophy

The last subgroup of FSHD is characterized by when symptoms of the condition begin rather than the genetic cause. Early-onset or infantile FSHD can develop from either the FSHD1 or FSHD2 mutation. It usually presents with facial weakness before age 5 and weakness in the shoulder or arms by age 10.

In comparison, 90% to 95% of all FSHD cases develop in adolescence or early adulthood, making the overall prevalence of early-onset FSHD about 1 in 200,000.

Symptoms

The symptoms of FSHD are generally the same regardless of which genetic mutation has caused the condition.

In most people with FSHD, the progressive muscle weakness that characterizes the condition starts around the eyes and mouth and spreads unevenly.

While the face, shoulders, and arms are the primary targets for the weakness caused by the condition, FSHD can also affect other parts of the body, including the abdomen.

The full spectrum of FSHD symptoms can include:

• Weakness in the face
• Weakness in the shoulders
• Weakness in the abdominal muscles
• Curvature of the spine
• Weakness that is greater on one side of the body
• Changes to the structure of blood vessels in the retina that lead to vision loss (Coats disease)
• Pain or inflammation in the joints or muscles
• Weakness in the hips or upper legs
• Hearing loss
• Breathing problems

Symptoms and their severity vary from person to person.

Causes

In most cases, FSHD is an inherited condition. It is caused by a genetic mutation that affects the proteins that make your muscles work properly.

In FSHD1, the genetic mutation is usually inherited in an autosomal dominant pattern, which means that only one parent has to carry the genetic mutation for the condition to develop.

FSHD1 can also develop spontaneously while fetuses are developing in the womb. This happens in about 10% to 30% of cases.

How FSHD2 is inherited is less clear, but experts believe that a mutation on chromosome 18 might be involved. As estimated, 60% of FSHD cases are sporadic or do not appear to be inherited.

It's also possible for people with FSHD to carry both the FSHD1 and FSHD2 mutations.

Diagnosis

FSHD is diagnosed based on a number of things, including:

• Your symptoms
• A physical examination
• A detailed personal and family history
• Genetic testing

In cases where there is no known family history of FSHD, other tests can be used to determine the cause of your symptoms, such as:

• Blood tests to check serum creatine kinase levels
• Tests that record the electrical response of your skeletal muscles (electromyography)
• Biopsy and microscopic examination of muscle tissue
  

Treatment

As with most forms of muscular dystrophy, there is no cure for FSHD. Your healthcare provider will need to see you often as the disease progresses to monitor for new areas that might be affected by muscle weakness.

You might need to have regular tests such as:

• Physical and occupational therapy assessments
• Vision screening
• Hearing tests
• Lung function testing
• Genetic counseling

The primary treatment for FSHD is exercise and physical therapy (PT). Nonsteroidal anti-inflammatory (NSAID) medications and other pain relievers can be used to treat chronic pain and inflammation.

Researchers are also looking at the potential for gene editing and new classes of medications as treatments for FSHD.

In rare cases, surgery to attach the shoulder blades to the chest wall is considered. However, most of the time, the movement challenges that are caused by FSHD can be managed with mobility and orthotic devices such as braces or wheelchairs.

Prognosis

Unlike other forms of muscular dystrophy, FSHD does not usually shorten a person's lifespan or cause severe disability. FSHD develops slowly and does not usually begin until early adulthood.

In most cases, about a quarter of people with typical FSHD will require a wheelchair or other mobility aid by the time they are in their 50s.

For people who have early-onset FSHD that began in childhood, the condition progresses more quickly. Children with FSHD sometimes need mobility assistance or require a wheelchair in their 20s or 30s—or even earlier in rare cases.

In addition to having earlier, more rapidly progressing symptoms, children whose FSHD begins early in life face a higher risk of complications like hearing and vision loss.

Coping

Living with chronic disease can be challenging, especially if you have a rare disease. If you have FSHD, know that there are organizations that can provide resources and support to you and your loved ones, including:

• FSHD Society
• Muscular Dystrophy Association
• National Organization for Rare Diseases

It's important to have a good support system and ask for help at home when you need it. Talk with your healthcare team about your needs. They can direct you to local care agencies and home health organizations to assist you.

If your current treatment regimen is not working well enough, you may want to consider enrolling in a research study or clinical trial.

Summary

Facioscapulohumeral muscular dystrophy (FSHD) is a chronic and progressive disease. It does not typically cause the severe disability and shortened lifespan seen with other dystrophies. However, people with more severe forms of the disease may still need to use a wheelchair or other aids eventually.

There is no cure for FSHD, but your healthcare provider can work with you to improve your strength and support your health, as well as try to slow muscle loss.

A Word From Verywell

Facioscapulohumeral muscular dystrophy (FSHD) can cause weakness in the muscles of the face, shoulders, and arms. The progressive weakness can also affect other parts of the body, but it is not usually as severe as other forms of muscular dystrophy. People in advanced stages of the disease may need a wheelchair or other mobility aids, but fatal complications are not common.

Having a good support system is important when it comes to maintaining a good quality of life with FSHD or any chronic medical condition. In addition, participating in a research study or clinical trial may help you improve your health and contribute to discovering new therapies.