Diseases of muscle Flashcards
Give the 5 limited symptoms of muscle disease?
1) Wasting
2) Pain
3) Cramping
4) Fasciculations
5) Weakness
What are the 5 clinical muscle investigations?
1) Clinical examination (neurological)
2) Electromyograph
3) Nerve conduction studies
4) MRI
5) Serum/ Blood investigations
Give 3 common sights of muscle biopsy?
1) Deltoid
2) Biceps
3) Quadriceps
What does the term limb-girdle muscular dystrophy refer to?
Group of rare inherited disorders which predominantly affect the muscles around the shoulder girdle and hip girdle causing progressive muscle weakness eg. Duchenne muscular dystrophy
What is the pattern of inheritance of Duchenne muscular dystrophy?
X linked recessive
What are the 4 clinical features of Duchenne muscular dystrophy?
1) Relentlessly progressive muscle wasting
2) Chair-bound by 12 years
3) Proximal muscle weakness
4) Hypertrophy of calves
What is the pattern of inheritance of Emery-Dreifuss Muscular dystrophy?
X linked recessive
What are the 3 clinical features of emery-dreifuss muscle dystrophy?
1) Weakness of proximal arm and distal leg muscles
2) Early contractures
3) Cardiomyopathy
What is the pattern of inheritance of core disease?
Autosomal dominance
Core disease is a defect of what kind of protein?
Myofribilar and internal cytoskeletal proteins
Duchenne muscular dystrophy is a disease of which part of the muscle?
Plasma membrane
When is core disease usually detected?
When the child starts walking
How is core disease defined?
The central core is a well demarcated zone in the center of a muscle fibre, devoid of normal histochemical activity.
In core disease, cores only occur in what type of fibres?
Type 1 fibres
Nemaline myopathy is a disease of what proteins?
Myofibrillar and internal cytoskeletal proteins
Nemaline myopathy has what kind of inheritance pattern?
Autosomal recessive
What are the 4 clinical features of nemaline myopathy?
1) Generalised neonatal hypotonia
2) Resp insufficiency
3) High arched palate
4) Kyphoscolioisis
Malignant hyperthermia is a disorder of what part of the muscle?
Ion channels and ion transporters
What is malignant hyperthermia?
Abnormal susceptibility to certain inhalational anaesthetics which leads to a prolonged rise in intracellular calcium ions leading to rigid contractions and elevation in body temp
What are the muscle biopsy changes in malignant hyperthermia?
Mild and non specific
Myotonic dystrophies are due to what kind of genetic defect?
Repeat expansion
What is the pattern of inheritance of myotonic dystrophy?
Autosomal dominant
What is the age of onset of myotonic dystrophy?
20-30 years
What are the 2 clinical features of myotonic dystrophy?
1) Myotonia and progressive weakness of facial muscles
2) Cardiac conduction defects
Fascioscapulohumeral dystrophy has what kind of inheritance pattern?
Autosomal domiant
When does fascioscapulohumeral dystrophy present?
In early adult life
In addition to the skeletal muscle effects, what are the 3 other clinical features of fascioscapulohumeral dystrophy?
1) Myocardium affected
2) Progressive deafness
3) Retinal vasculopathy
What is the pathology of myasthenia gravis?
Autoimmune disease with Ab usually IgG, against the acetylcholine receptor
Is muscle biopsy an appropriate diagnostic test for myasthenia gravis? What changes may be seen on biopsy?
NOT an appropriate diagnostic test
May see mild changes of denervation atrophy
What is Eaton-Lambert Myasthenic Syndrome?
Rare, non metastatic manifestation of malignancy - usually oat cell carcinoma of the bronchus
Are any changes seen on biopsy in Eaton-lambert Myasthenic Syndrome?
No specific changes seen
Mitochondrial myopathies are related to what defect?
Respiratory chain defects
What are the 3 histological changes in mitochondrial myopathy?
1) Ragged red fibres
2) Accumulation of lipid on Oil red O stain
3) Biopsy may be relatively normal
What is dermatomyositis?
Inflammatory myopathy responsible for chronic debilitating disease, associated with a scaly rash
What is the most common type of drug-induced myopathy?
Steroid induced myopathy
Steroid induced myopathy leads to what 2 histological changes?
1) type 2 fibre atrophy
2) Increase in lipid droplets
What is the most serious drug induced myopathy caused by?
Heroin and ecstasy
What are the 3 clinical features of heroin and ecstasy induced myopathies?
1) Necrotising myopathy causing: rhabdomyolysis
2) Myoglobinuria
3) Renal failure
In addition to steroids, heroin and ecstasy what other drug can cause myopathy?
Statins
What is motor neuron disease characterised by?
Progressive disease of middle to old age which is characterised by widespread degeneration of motor neurons
What cells are involved in MND? 3
1) Anterior horn cells
2) Brain stem nuclei
3) Betz cells
What are the clinical features of MND?
Upper and lower motor neuron signs with wasting associated with spasticity and brisk reflexes
Which 3 endocrine disorders can lead to myopathies?
1) Glucocorticoid
2) Thyroid
3) Parathyroid
4) Growth hormone
5) Insulin
