Muscular Dystrophy

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What is Muscular Dystrophy?

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The Muscular Dystophies are a group of hereditary and genetic muscle diseases mainly characterised by the presence of progressive skeletal muscle weakness. There is usually a defect or deficiency in essential muscle proteins which is accompanied by the death of muscle cells and tissues. Cardiac and smooth muscle may be affected in some types of muscular dystrophy. The major types of muscular dystrophy include:

Becker's muscular dystrophy (BMD) - usually noticeable at adolescence

Congenital muscular dystrophy (CMD) - usually noticeable at birth

Distal muscular dystrophy

Duchenne muscular dystrophy (DMD)

Emery-Dreifuss muscular dystrophy (EDMD)

Facioscapulohumeral dystrophy (FSHD)

Fukuyama congenital muscular dystrophy (FCMD)

Limb-girdle muscular dystrophy (LGMD)

Myotonic muscular dystrophy

Oculopharyngeal muscular dystrophy

Severe childhood autosomal recessive muscular dystrophy

Who gets Muscular Dystrophy?

The muscular dystophies are the most common form of hereditary disease. The most common form of muscular dystrophy is Duchenne muscular dystrophy, followed by facioscapulohumeral and myotonic. The approximate incidence is as follows:

DMD: 1 in 3300 live male births

BMD: 1 in 18000 live male births

Congenital myotonic dystrophy: 1 per 10 000 births

FSFHD: Prevalence of 1 in 20,000

Males are more affected than females. Depending on the type of muscular dystrophy, it can be first apparent from birth right through to adolescence.

Predisposing Factors

The muscular dystrophies are all hereditary conditions thus the main predisposing factor is genetics. For X-linked muscular dystrophies (the way in which it is inherited), being male has a much larger predisposition for the disease whilst females may carry the gene but not have the disease. For autosomal dominant muscular dystrophies, an affected parent is a increased risk factor.

Progression

The natural history of muscular dystrophy depends on the type. In DMD and some cases of BMD there is progressive weakness, contractures and the inability to walk. A
kyphosis (back deformity) may develop which can lead to respiratory difficulty and hence an early death (DMD~16 years, BMD~42 years). With some other types of muscular dystrophy there is slow progression and thus a near normal lifespan.

Some complications that may arise from muscular dystrophy (depending on the type) include cardiac arrythmias, hypertension, dysphagia, malignant hyperthermia, respiratory problems, cataracts and hearing loss.

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