Clinical Picture
FSHD is a very heterogeneous disorder and each person, even
people within the same family, may differ slightly in the severity
of FSHD. In severe cases, an infant may present with very weak
muscles. However, FSHD may be so mild that adults may be unaware
they are affected until a family member with more severe symptoms
seeks medical attention.
Both males and females are affected equally with FSHD. By age
20, nearly all affected individuals have some level of muscle
weakness due to atrophy of the muscles. Most affected individuals
first notice facial weakness and have difficulty with smiling,
whistling, closing their eyes, and certain facial expressions.
Scapular winging also commonly occurs in individuals with FSHD.
This occurs because the shoulder muscles weaken and do not hold
the scapula in place, which may cause them to protrude. Some
people with FSHD have forward sloping of their shoulders and
difficulty raising their arms over their head. The pectoral
muscles of the chest and abdominal muscles may become weak,
however, muscles involved in breathing and swallowing are usually
not affected. Difficulty in walking occurs if the lower leg
and hip muscles weaken. Muscular weakness is often more noticeable
on one side of the body and is therefore said to be asymmetrical.
Approximately 50% of those with the disorder retain the ability
to walk throughout their lives.
The progression of this disease is slow, with muscular weakness
increasing over years. Sometimes there can be rapid spurts
of progression that soon plateau. A minority of patients require
a wheelchair because of difficulty walking. The extent to
which muscle weakness will impact a person’s ability
to function is very variable and unpredictable. Unfortunately,
at this time there is no cure or treatment that can prevent
symptoms of FSHD. However, there are medical management strategies
that can help to maintain or improve muscular function, including
orthopedic supports and sometimes surgery to improved function
in the shoulder area.
Ways a person gets FSHD:
There are three main ways that an individual can get this disorder.
- A parent with FSHD passed on the mutated gene to his or
her daughter or son.
- A deletion or other genetic alteration occurred in the
sperm or egg that formed the embryo by chance (sporadic
mutation). De novo mutations account for nearly 30%
of cases.
- A parent has germline mosaicism, which is generally a
very rare genetic phenomenon. The effect of mosaicism varies
in every person. Some mosaic individuals may show no signs
of the disease, but are at risk to pass on FSHD to their
children if their sex cells contain the deletion. The exact
risk of passing on FSHD is unknown, but can be as high as
50%. Other mosaic individuals may have a severe case of
FSHD.
Genetic Testing
There is genetic testing available for FSHD, which takes on
average 2 – 6 weeks for results. About 95% of people who
have been diagnosed with FSHD have a deletion on chromosome
4, however the exact gene that causes FSHD is still unknown.
Regarding deletions that cause FSHD, the severity and age of
onset of symptoms seems to correlate with the amount of genetic
material that is missing in the DNA. A small number of people
genetically tested for FSHD do not have a deletion, but have
a different form of a mutation, such as a tandem repeat mutation.
We know that there is a genetic marker for FSHD on 4q35 and
that this tandem repeat tends to be smaller in individuals affected
with FSHD. The smaller the repeat, the more severe the disease
tends to be and the earlier the onset.
- Normal repeat range: 10 to >100 copies
- Borderline repeat range: 9 to 10 copies
- FSHD repeat range: 1 to 8 copies
The decision to be genetically tested is a very important
and personal decision. A patient considering this step should
speak with a genetic counselor.
Support
After your patient is diagnosed with FSHD, he or she is likely
to feel overwhelmed. It may be helpful to let your patient know
that support is available. Contact your local Muscular Dystrophy
Association Clinic for more information, or visit the web site
at www.mdausa.org.
Additionally, visit the Links section
on this Web site to learn more about other support and information.
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