MDF Magazine Issue 62 7 August 2020 (7)

Prof Amanda Krause, MBBCh, PhD MB BCh,
Medical Geneticist/Associate. Professor.
Head: Division of Human Genetics.
National Health Laboratory Service (NHLS)
& The University of the Witwatersrand.
Please e-mail your questions about genetic counselling to national@mdsa.org.za.
What is muscular dystrophy?
Muscular dystrophy is the name given to a group of diseases which cause progressive weakness and wasting of the muscles. They are caused by faults
in a group of genes and are thus genetic disorders. The normal function of these genes is to create the protein support backbone of muscle cells and
maintain their normal function.
Thus when these genes are faulty, degeneration of the skeletal (voluntary) muscles that control movement results and progressive weakness follows.
Depending on which particular gene is faulty in an individual and the severity of the fault, muscular dystrophy can first manifest in infancy or up to
middle age. In some forms of this disease, the heart and other organs are also affected. The disorders differ in terms of the distribution and extent of
muscle weakness, age of onset, rate of progression, and pattern of inheritance. The prognosis for people with muscular dystrophy varies according to
the type and progression of the disorder.
It is important that a specific genetic diagnosis be made for an individual with muscular dystrophy, so that management can be as specific as possible.
A specific genetic diagnosis also allows questions around prognosis and risks for other family members to be answered more precisely.
Are there any other diseases with the same symptoms as muscular dystrophy?
Muscular dystrophies are, by definition, genetic disorders. There are, however, other muscle conditions which may present with overlapping symptoms.
These can include conditions where the muscles become inflamed or where there is muscle wasting due to underlying endocrine problems, for example
hypothyroidism. These conditions can generally be distinguished from muscular dystrophies with appropriate clinical and laboratory investigation.
What is the role of creatine kinase (CK) determination in the evaluation of muscular dystrophy?
Creatine kinase (CK) is an important protein in muscle cells. It is also found in the heart, brain and other tissues, but at lower levels. Increased amounts
of CK are released into the blood when there is muscle damage. CK levels can also be increased when there is heart muscle damage, for example with
a myocardial infarction. This test measures the amount of creatine kinase in the blood.
Persistently high CK levels can be found in many muscular dystrophies as the CK is released as the muscle cells break down. However, levels are not
increased in all muscular dystrophies. In an individual with a muscular dystrophy, CK levels may be raised before weakness is evident clinically. In
inflammatory muscle conditions CK levels can also be very elevated.
Doctor’s
In addition, there are many other conditions where CK levels are found to be elevated, including after strenuous exercise and trauma and in some
endocrine disorders. Certain medication may also increase CK levels. Thus an elevated CK level does not confirm a diagnosis of a muscular dystrophy.
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