Becker's dystrophy has a similar prevalence 1:3500 males. Clinical features
Onset is later than Duchenne - aged 10 years, remaining ambulant until the 3rd or 4th decade. ECG abnormalities occur in 40% but are rarely severe.
Calf hypertrophy is common. Limb girdle muscles may be selectively involved. Muscle biopsy in contrast to Duchenne shows dystrophin but in reduced amounts. EMERY-DREIFUSS DYSTROPHY
Onset in childhood/adolescence. Contractures of elbows and neck are associated with periscapular and biceps weakness (with spared deltoids). Cardiomyopathy with conduction abnormalities can be life threatening. Muscle biopsy is non-specifically abnormal. AUTOSOMAL DOMINANT DYSTROPHIES FASCIOSCAPULOHUMERAL DYSTROPHY
This is inherited as an autosomal dominant trait. Described by Dejerine (1885) it is referred to as Dejerine's dystrophy.
Abortive forms of this condition in which selective muscle involvement occurs (e.g. unilateral shoulder muscle) may 'mask' the dominant mode of inheritance. Incidcnce: 1-2 per 100 000.
The expression of disease is variable and often mild. Onset in first or second decade. Initially the lower half of the face is involved -cannot purse lips or whistle - then spread into trapezius and pectorals occurs with scapular 'winging'. Lumbar lordosis develops from spinal muscle weakness. Pelvic musculature and quadriceps may eventually become involved. Dromedary or camel-backed gait with protrusion of the buttocks is characteristic. Calf and deltoid muscles may be hypertrophic.
Unlike Duchenne dystrophy the clinical course is slow and arrest of progression may occur.
In some cases weakness of facial muscles is noted in childhood without spread to other muscles until middle age. Cardiac muscle is not involved. Sensorineural deafness and retinal vascular changes (telangiectasis and detachment) may occur. Life expectancy in this condition is normal. EMG studies show myopathic changes. Muscle enzymes may be normal or slightly elevated.
Muscle biopsy shows increased fibre diameter; a cellular response of lymphocytes and plasma cells may be present between muscle fascicles.
There is no specific treatment other than general support with genetic guidance.
This is an autosomal dominant or recessive disorder with involvement of proximal upper limb and distal lower limb muscles. Onset is in adult life with foot drop (anterior tibial and peroneal muscle groups). Weakness next affects the upper limbs with spread from scapular muscles into deltoid, biceps and triceps. The disease runs a benign non-disabling course. Cardiac muscle involvement may occur in later life. A more aggressive X-linkcd form of this dystrophy has been described.
The creatine kinase enzyme is elevated.
The electrocardiogram may be abnormal with atrial arrhythmias.
EMG studies show myopathic changes.
Muscle biopsy will show non-specific myopathic features.
Differentiation from spinal muscular atrophy and inflammatory myopathy with the same distribution of muscle involvement may require EMG and biopsy.
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