Facioscapulohumeral Muscular Dystrophy
Fact Sheet # 07
Is FSHD also known by other names?
Facioscapulohumeral Muscular Dystrophy is generally just referred to by its abbreviation: FSHD. Previously, this disorder was also known as Landouzy-Dejerine disorder, after the two physicians that first described it in 1886.
What is FSHD?
FSHD is the third most common form of muscular dystrophy, with an estimated prevalence of 1 in 20 000. It affects mainly muscles of the face (facio), shoulder (scapulo) and upper arm (humeral) region, as indicated by the name. However, the name is misleading as muscles of the leg are often also involved.
What causes FSHD?
FSHD is due to a deletion (missing piece) of DNA on chromosomes 4. The region in which the deletion is located is almost at the tip of chromosome 4’s long arm, at position 4q35. A piece of DNA that is 3.2 kb (3200 bases) in length, is repeated several times in this region of the chromosome - let us assume for the sake of illustration it is repeated 20 times. In individuals affected with FSHD some of the repeats are missing (a deletion) and thus only (let us assume) 15 copies of the repeat are present. A deletion of 5 copies thus caused the observed FSHD in our example. Although it is known where the gene is located, the gene responsible for FSHD has not yet been identified. This array of tandem (right after each other, with no spaces) repeats is used to diagnose individuals affected with FSHD, since we know that shorter repeat lengths are associated with FSHD. It is known if, and indeed how, the repeat may be involved in causing FSHD. This change in the DNA is present at birth, but its effect only becomes visible later on in life. However, the gene is believed to cause abnormal structure of the muscle.
What are the symptoms?
Individuals affected with FSHD usually begin to notice muscle weakness during their teenage years. FSHD can generally be recognised and diagnosed by the age of 20, in most cases. However, the clinical diagnosis is difficult and confirmation of the diagnosis (via a DNA test) is preferred. It is important to remember that the age of onset can vary, and the degree to which the symptoms are present is also highly variable. In some instances, muscle weakness may be very subtle, even in individuals who are 60-70 years of age. Occasionally a child (even as young as before the age of 5) or even an infant has symptoms (infantile FSHD). However, these are the exception to the rule. In very mild cases, it may not be possible to detect progression of weakness. In general the progression is evident but slow and could sometimes level off. There is often difficulty raising the hands above shoulder level causing problems with combing the hair or reaching high shelves. Lifting heavy objects may be difficult, even below shoulder level. Some individuals first notice a problem whilst doing sport or recreation exercises. One of the most striking features of FSHD is the "winging" (see 5) of the scapula. In more severely affected individuals hearing loss, or partial hearing loss, is often observed.
Which muscles are affected?
The face, shoulder and upper arm region is involved, as well as the muscles of the leg. As the name implies there is facial weakness (in varying degrees) that may result in the inability to close the eyes properly and to whistle. The shoulders droop and there is increasing difficulty in raising the arms. A notable feature is that the shoulder blades become very prominent for which the term “winging” is often used. At onset, muscle weakness could often affect one side more than the other. As the disorder progresses the pelvic muscles may also become affected which results in a waddling gait and lordosis (pelvis pushed forward). Lower limbs may weaken resulting in foot drop and a tendency to trip, as well as finding it difficult to climb stairs.
How is FSHD inherited?
FSHD is an autosomal dominant neuromuscular disorder. This implies that an affected parent (either one) transmits one copy of the faulty gene. Children of either sex can be affected and each child of an affected parent has a 50% chance of being affected. The gene, located on chromosome 4, has not yet been identified. In some rare cases, the mutation that causes FSHD is a new mutation (spontaneous mutation) and no family history of FSHD might be present. Individuals affected in this manner can then in turn pass the mutation to their children. As this is a genetic condition, genetic counselling is strongly recommended. Genetic counselling provides information on the inheritance pattern, risks to other family members, prognosis, psycho-social support, as well as information about diagnostic testing, carrier testing, preclinical and prenatal testing (where available).
How is FSHD diagnosed?
FSHD can be diagnosed on the clinical (neurological) or genetic (DNA) levels. Generally clinical diagnoses are made first, and then confirmed via a DNA test. Detection of a deletion of part of a 3.2 kb repeat in the DNA on chromosome 4q35 (see 3 above) is used to diagnose FSHD on the molecular level. It appears that individuals with more severe symptoms have a larger deletion, than individuals who are only mildly affected - although this cannot be used in individual cases to predict severity.
Is there a cure?
To date, there is no cure or specific drug treatments for FSHD. Regular mild exercise is beneficial (especially swimming). It is essential to keep your weight down in order to reduce stress on already weakened muscles.
Is there any treatment?
The scapula muscles that attach the shoulder blades to the chest are often very weak and this leads to difficulty in lifting the arms. The surgical procedure of scapular fixation (fixing the shoulder blades to the ribs at the back) has in the past enabled some severely affected individuals to regain some use of their arms. Because prolonged immobilisation of limbs could increase the weakness of disused muscles, combined assessment from a neurologist and an orthopaedic surgeon prior to this type of surgical correction is essential.
Is there a risk during anaesthesia?
It is always recommended that the presence of a muscular disorder be mentioned to your doctor.
Has research been conducted on FSHD in South Africa?
Yes, FSHD is being investigated on the DNA (molecular) level in the Department of Human Genetics, and at the clinical level in the Department of Neurology - both at the University of Pretoria. An FSHD clinic is conducted every Thursday at the Dept. of Neurology where individuals are clinically assessed, and genetic counselling is provided. It is envisaged that a DNA diagnostic service will be established after completion of the current study of FSHD on the molecular level.
Please contact your local MDF office for further information.
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