Muscular Dystrophy Association Inc, 36 - 38 Henley Beach Road, Mile End SA 5031
Postal address: GPO Box 414, Adelaide SA 5001| Email: info@mdasa.org.au | Tel: 08 8234 5266 | Fax: 08 8234 5866

What is Muscular Dystrophy?

 

Muscular Dystrophy refers to a group of neuromuscular disorders affecting approximately 1 in 1,000 of the population. Although each disorder is slightly different, all neuromuscular disorders have three features in common:

They are hereditary

 

By definition, all muscular dystrophies are genetic, but they are not always inherited. In other words, there is not always a history of muscular dystrophy in a previous generation of an affected person’s family for a number of reasons. First a person may be affected by a genetic defect which has just occurred in a family for the first time, in one egg or sperm of his or her parent. This is called a new mutation. Secondly, a parent may have been so slightly affected by the disorder that it was unnoticed and may not have been diagnosed, even by an experienced physician. Thirdly, one important mode of inheritance, autosomal recessive, very seldom affects more than one generation.

 

They are progressive

 

Some forms of muscular dystrophy progress more rapidly than others. Also, people with the same sort of muscular dystrophy may have different rates of progression, even within the same family. And each produces a characteristic selective pattern of weakness of muscle groups.

 

Usually the characteristic pattern of weakness and the resulting disability suggests the diagnosis. Often there are typical effects on posture and gait, affecting how a person stands and walks.

 

    • When the muscles of the face are affected, the facial expression is altered in a recognizable way.
    • Enlargement of calf muscles and sometimes other muscles are typical of some muscular dystrophies.
    • Myotonic Muscular Dystrophy is associated with delayed muscle relaxation, called myotonia.
    • Cramps occur in some muscular dystrophies, especially Becker Muscular Dystrophy. Otherwise, pain is not normally a feature of muscular dystrophies.

These disorders are separated into three main groups – dependent on the origin of where the communication breaks down to cause the muscle weakness.

 

    • Disorders of voluntary muscles (muscular dystrophies and myopathies)
    • Disorders of the motor neurone
    • Disorders of the nerve-muscle junction

     

Disorders of the Voluntary Muscles

 

Muscular Dystrophies

 

The muscular dystrophies are a group of inherited disorders which cause progressive degeneration (breakdown) of the muscles. They affect both children and adults. Signs of muscular dystrophy appear at any age, but most often in young people. For example, Duchenne Muscular Dystrophy is usually first noticed in toddlers, Becker’s Muscular Dystrophy in childhood or adolescence and Myotonic Muscular Dystrophy in adulthood.

 

    • Duchenne Muscular Dystrophy (Pseudo-hypertrophic)
    • Becker Muscular Dystrophy
    • Facioscapulohumeral (FSH) Muscular Dystrophy (Landouzy-Dejerine)
    • Limb-Girdle Muscular Dystrophy
    • Opthalmoplegic Muscular Dystrophy
    • Distal Muscular Dystrophy
    • Muscular Dystrophy of Late Onset
    • Myotonic Muscular Dystrophy (Steinert’s Disease)Congenital Muscular Dystrophy
    • Emery-Dreifuss Muscular Dystrophy
    • Oculopharyngeal Muscular Dystrophy

 

Myopathies


These disorders are caused by inherited abnormalities of muscle chemistry, or by exposure to certain toxic substances. Some are congenital, (present at birth), whilst others are caused by inflammation in the muscle (dermatomyositis) and may respond to drug treatment. All myopathies produce progressive weakness.

 

    • Inflammatory Myopathies
    • Polymyositis
    • Dermatomyositis
    • Myositis Ossificans
    • Inclusion Body Myositis

 

Myotonias

 

    • Myotonia Congenita (Thomsen’s Disease)
    • Paramyotonia Congenita

 

Metabolic Disease of Muscle

 

    • Phosphorylase Deficiency (McArdle’s Disease)
    • Acid Maltase Deficiency (Pompe’s Disease)
    • Phosphofructokinase Deficiency (Tarul’s Disease)
    • Debrancher Enzyme Deficiency (Conn’s or Forbe’s Disease)
    • Carnitine Deficiency
    • Carnitine Palmityltransferase Deficiency
    • Periodic Paralysis

 

Less Common Myopathies

 

    • Central Core Disease
    • Nemaline Myopathy
    • Mitochondrial Disease
    • Myotubular Myopathy
    • Idiopathic Myopathy
    • Malignant Hypertheria (Hyperpyrexia)


Disorders of the Motor Neurone

 

Disorders of the motor neurone (or the nerves controlling the muscles) are a group of inherited or acquired disorders which may commence at any age. Like the muscular dystrophies these disorders may be slowly or rapidly progressive with varying degrees of paralysis.

 

A major member of this group are the Spinal Muscular Atrophies. The basis of these disorders is caused by a degeneration in, or an injury to, a nerve which supplies a muscle or group of muscles. As a result of the nerve damage, muscle tissue will weaken and become ‘withered’ or ‘shrunken’. This is referred to as ‘atrophy’.

 

    • Spinal Muscular Atrophies
    • Motor Neurone Disease (Lou Gehrig’s Disease/Amyotrophic Lateral Sclerosis)Leukodystrophies (various forms)
    • Juvenile Progressive Muscular Atrophy (Kugelberg-Welander)
    • Benign Congenital Hypotonia
    • Charcot Marie Tooth Disease (CMT)
    • (Peroneal Muscular Atrophy)
    • Friedreich’s AtaxiaDejerine-Sottas Disease (Progressive Hypertrophic Interstitial Neuropathy)

 

Disorders of the Nerve-Muscle Junction

 

Disorders of the nerve-muscle junction occur as a result of the nerves controlling the muscles, not being able to transmit their normal number of messages to the muscles. As a result, this causes weakness and fatigue. The main disorder in this group is Myasthenia Gravis.

 

The disorder can affect people of all ages and either sex; however it is much more common in women. This disorder is not contagious, nor is it thought to be inherited, but occurs in certain families more frequently than can be explained by chance alone. Drug treatment is often effective, allowing many people to lead normal lives.

 

    • Myasthenia Gravis
    • Eaton-Lambert Syndrome
    • Congenital Myasthenic Syndrome