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Myotonic Dystrophy
Fact Sheet # 20
Muscular Dystrophy Foundation (MDF) of South Africa
Mission statement:
The Muscular Dystrophy Foundation of South Africa is a non-profit organisation which supports
people affected by muscular dystrophy and neuromuscular disorders.
1.
Is Myotonic Dystrophy also known by other names?
Yes, Myotonic Dystrophy is also known as Steinert’s disorder or Dystrophia Myotonica.
2.
What is Myotonic Dystrophy?
Myotonic dystrophy is the most common adult form of muscular dystrophy - the general term for a
group of hereditary disorders where the most prominent feature is muscle weakness and
progressive wasting of voluntary muscles. Myotonic Dystrophy is associated with myotonia
(delayed relaxation of muscles after contraction). Myotonic Dystrophy can affect the tissues and
organs of many body systems in addition to the voluntary muscle system. Clinical features include
cataracts, disturbance of the heart rhythm, hormonal problems, frontal balding (in males), testicular
atrophy, difficulty in swallowing (dysphagia) and learning difficulties in children. Consequently,
myotonic dystrophy may present itself in a variety of ways. While affecting predominantly adults, it
also occurs in infancy and childhood. Congenital Myotonic Dystrophy is the early childhood form of
Myotonic Dystrophy.
3.
What causes Myotonic Dystrophy?
A faulty gene that is located on chromosome 19 causes myotonic dystrophy. This defective gene
has a change (mutation) in one end region of the gene, which is unstable. This change is the
expansion of a series of three building blocks (nucleotides) of DNA. This series of three
nucleotides is called a "triplet" repeat. The expansion of the triplet repeats is from just a few copies
in healthy (unaffected) individuals, to several hundreds in individuals affected with myotonic
dystrophy. Once the change is established it often (not always) increases in the following
generations, leading to an increase in severity of the disorder as the repeat increases in size. The
normal gene produces a protein that is likely to be important in membrane function of the muscle
and other organs. In myotonic dystrophy the expansion in the gene is thought to result in an
abnormal function of the protein.
4.
What are the symptoms?
Symptoms may present at birth, in childhood or at any age. Myotonic dystrophy can affect the
tissues and organs of many body systems in addition to muscle. The following should be noted:

Many affected individuals show visible signs of the disorder before the age of 20 but a
significant number of individuals do not develop clear-cut symptoms until after 50. However,
when myotonic dystrophy is suspected (because it is present in other members of the
family) careful examination may reveal typical abnormalities before the individual complains
of either weakness or myotonia. The course of the disorder can vary widely between
individuals within a single family. The range of symptoms is from very mild, so that the
individual does not know they have the disorder, to severe, where death may occur within
20 years after appearance of the initial symptoms.

Muscle weakness and muscle wasting. The first muscles to be affected are those of the
face, neck, hands, forearms and feet. Weakness is slowly progressive but most patients
remain mobile.

Muscle stiffness or ‘myotonia’ (delayed relaxation of muscles after contraction) is
characteristic, especially affecting the hands.

Symptoms involving the other organ systems, include blindness due to cataracts,
swallowing difficulties, frontal balding in men, diabetes, heart problems (due to an irregular
heart beat) and testicular atrophy may occur.

Symptoms vary between individuals. Individuals who present at a young age are more
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
likely to develop muscular problems.
Congenital myotonic dystrophy is the severest form and can be fatal. It presents at birth.
Infants have profound difficulty with sucking and swallowing and may have severe
respiratory difficulties. Motor development is delayed and they may show some learning
problems and may be developmentally delayed.
5.
Which muscles are affected?
Muscles in the face, jaw and neck area are mainly involved. The large, weight-bearing muscles of
the legs and thighs are much less affected. Myotonia or muscle stiffness characteristically affects
the hands. Muscle of the oesophagus can also be involved which leads to swallowing problems.
Cardiac (or heart muscle) can also be affected.
6.
How is Myotonic Dystrophy inherited?
Myotonic dystrophy can be transmitted from generation to generation by individuals who
themselves have inherited the defective gene and have the disorder. Since the defective gene is
transmitted in an autosomal dominant pattern, only one faulty myotonic dystrophy gene, derived
from either the father or mother, is required to produce the disorder in a child. There is therefore a
50% chance that a child will be affected. Since a parent can be more mildly affected than a child, it
is not unusual for a child to present with myotonic dystrophy before the diagnosis has been made
in the affected parent. Further, if a father is the transmitting parent, a child is likely to be similarly
affected to his father. However, if the mother is the transmitting parent, she may have a child who
may present as early as birth with myotonic dystrophy. 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).
7.
How is Myotonic Dystrophy diagnosed?
A physical examination will usually reveal the typical pattern of muscle weakness and wasting as
well as the presence of myotonia. Special laboratory tests, which may include a muscle biopsy,
can confirm the diagnosis. The myotonic dystrophy gene has been characterised and therefore a
diagnosis can be made at the genetic level, by providing a blood sample. The test is positive in
100% of individuals with the condition. Thus, muscle biopsies should no longer be used to confirm
a diagnosis of myotonic dystrophy. The genetic test can be carried out before any symptoms arise
and can therefore also be useful for prenatal or preclinical diagnosis.
8.
Is there a cure?
No, unfortunately no cure has yet been found for myotonic dystrophy.
9.
Is there any treatment?
No specific treatment has yet been found for the muscle weakness and wasting in myotonic
dystrophy although ankle and leg braces can help to support muscles as weakness progresses.
Medications are advised for particular symptoms, such as muscle stiffness (myotonia) or for heart
irregularity. Pacemakers may also be necessary for heart irregularities in some instances.
10.
Is there a risk during anaeshesia?
Yes, anaesthesia is a risk for patients with myotonic dystrophy. It is therefore essential that your
family doctor, surgeon and anaesthetist be told that you have this condition, even if you are only
mildly affected. If surgery is necessary, it should be carefully planned and done in a hospital with
proper back-up. The main problems are because of weak breathing muscles and sensitivity to
anaesthetics and drugs used, as well as the disturbances in heart rhythm. It is always
recommended that the presence of a muscular disorder be mentioned to your doctor.
11.
Is there any research conducted on Myotonic Dystrophy in South Africa?
Extensive research has been conducted on myotonic dystrophy at the Department of Human
Genetics, SAIMR and University of the Witwatersrand. International researchers are working on
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how the change in the gene and protein results in this muscle disorder.
12.
The role of the Muscular Dystrophy Foundation in South Africa
The MDF supports individuals affected by muscular dystrophy and their families by offering
emotional support, information - including a series of fact sheets, referrals to genetic counselling
and other clinics, formation of support groups, assistance with special equipment, when possible,
as well as financial support for research projects in muscular dystrophy in South Africa. Creating
public awareness for muscular dystrophy is also an important aspect of our work, since the MDF
relies solely on contributions from its members and other donors to provide an on-going support
service. Through our newsletter members are kept informed of all the activities and receive
national and international research updates. Please contact any office of the MDF if you require
information about any of our activities or programmes.
13.
Support group or contact person
Jean Walter
(021) 782-1895
Christien Stols
(011) 415-1812
If you are unable to contact any of these individuals, please contact the MDF.
14.
Where can we find assistance?
Please contact your local MDF office for further information.
National Office
Cape Branch
P.O. Box 1535, Pinegowrie, 2123
P.O. Box 13449, Mowbray, 7705
Tel: (011) 789-7634, Fax: (011) 789-7634
Tel: (021) 448-8766, Fax: (021) 448-8766
email: [email protected]
email: [email protected]
Gauteng Branch
Kwazulu-Natal Branch
P.O. Box 1535, Pinegowrie, 2123
P.O. Box 290, New Germany, 3620
Tel: (011) 789-7635, Fax: (011) 781-3935
Tel: (031) 701-3801, Fax: (031) 701-3801
email: [email protected]
email: [email protected]
Local Clinics:
Please contact your local MDF branch for further information.
General Information:
Independent Living Centre (ILC): (011) 482-5476
Disability Info and Care (DIC): (011) 917-3284
Parking Concessions: Application to the Traffic Department of our your Local Authority.
Criteria: (a) if you need the extra width as provided by the special parking bays, or
(b) if you have a problem with walking long distances.
Special Equipment:
Phone either ILC or DIC for information on where to get special equipment.
MDF Website:
Please visit our MDF website (www.mdsa.org.za) for muscular dystrophy news updates.
15.
Please note
The treatments and drugs mentioned in this fact sheet are for information purposes ONLY. Please
consult your physician or other health care specialist for information regarding the use of any of the
above. The MDF encourages duplication of this fact sheet, under the following condition: that it is
duplicated in its entirety - including the MDF logo and full text. Only individuals authorised by the
MDF may make changes to this fact sheet (the information "updated by" and "last update" should
be completed). Alterations to this fact sheet by any other party are strictly prohibited.
______________________________________________________________________________________________
This fact sheet was adapted from the following source(s): Fact sheet(s) of the Muscular Dystrophy Group of Great
Britain and Northern Ireland.
Compiled by: MDF-Gauteng Branch
Updated by: MDF-Gauteng Branch
Approved and Released by: National Office of the MDF
Last update: 30 May 2000
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