Diseases of Muscle Flashcards
What are the symptoms of muscle diseases?
Wasting Pain Cramping Fasiculations Weakness
What investigations are used to diagnose muscle diseases?
Clinical neurological examination
Electromyography - records electrical activity in muscles
Nerve conduction studies - tests peripheral nerves
MRI
Serum/Bloods- antibodies
What are the 3 different origins for muscle disease?
Neurogenic muscle disease - brain problems
Motor end-plate disorders e.g. myasthenia gravis
Primary muscle (myopathies) - destructive/non destructive
Where is a biopsy for suspected muscle disease usually taken from?
Quadriceps
Needle/core sample removed
Muscular dystrophies are normally due to a lack of which protein?
Sarcolemma
Duchenne muscular dystrophy and limb girdle muscular dystrophy are diseases of what?
the plasma membrane
Duchenne Muscular Dystrophy has what kind of inheritance?
Sex linked
Recessive
What protein is lacking in Duchenne Muscular Dystrophy?
dystrophin
How does Duchenne Muscular Dystrophy present (inc histologically)?
Progressive proximal wasting of muscles Hypertrophy of calves Loss of muscle mass Fibers hypertrophy due to muscle loss Immature fibers Fibrosis
Emery-Dreifuss Muscular Dystrophy has what kind of inheritance?
X linked recessive
How does Emert-Dreifuss Muscular Dystrophy normally present?
Weakness of proximal arm and distil leg
Early contractures
Cardiomyopathy
What 2 conditions is limb girdle muscular dystrophy similar to and needs to be excluded from?
Spinal muscular atrophy
Bone mineral density
Core diseases and nemaline myopathies come under dysfunction to what protiens?
Myofibrillar and internal cytoskeletal proteins
Core diseases have what kind of inheritance?
Dominant
The central core is where and only occurs in which type of fibre?
Zone in the center of a muscle fiber
Type I
How does central core disease present histologically?
Variation is fibre size
Every fibre contains 1 or more cores
No mitochrondia
How does Nemaline myopathy present? (inc histologically)
Generalised neonatal hypotonia - low muscle tone Respiratory insufficiency High arched palate Kyphoscoliosis Abnormal Z band with rod bodies attached
How is Nemaline myopathy inherited?
Autosomal recessive
Malignant hyperthermia is what type of defect?
Ion channel and ion transporter defect
What is malignant hyperthermia?
Abnormal susceptibility to certain anesthetic agents
Prolonged rise in intracellular Ca - rigid contractions/elevation in body temp
How does malignant hyperthermia present histologically?
moderate increase in central nuclei
Occasional fibers contain cores
Myotonic dystrophies and facioscapulohumeral dystrophy are defects of what?
Myopathies based on complex molecular defects
Myotonic dystrophies = repeat expansion diseases
Facioscapulohumeral dystrophy = large telomeric deletion disease
How is myotonic dystrophy inherited?
Dominantly
How does myotonic dystrophy present symptomatically?
Myotonic and progressive weakness of facial muscles - long face
Cardaic conduction defects
How does myotonic dystrophy present histologically?
Atropy of type I fibres Type II hypertrophy Central nuclei Moth eaten and targetoid fibres Ring fibres
How is Facioscapulohumeral dystrophy inherited?
Dominantly
How does Facioscapulohumeral dystrophy present?
Facial/shoulder muscle weakness Assymetrical weakness Affects myocardium Progressive deafness Retinal vasculopathy
What is myasthenia gravis?
Autoimmune disease
IgG antibodies against Ach receptors
What is Eaton-Lambert Myasthenic syndrome?
Autoimmune
Antibodies against Ca voltage gated ion channels
How do mitochondrial myopathies present histologically?
Ragged red fibres
Accumulation of lipid
Dermatomyositis is what type of myopathy?
Immune and infectious myopathies
What is Dermatomyositis and how does is present?
Inflammation of the skin and underlying muscle tissue Autoimmune/cancer Scaly rash Discoloration Swelling
How does Dermatomyositis present histologically?
Mononuclear cells infiltrate the muscle - fiber necrosis/fibrosis
Inflammation where B cell predominant
What are the most common drugs that induce a myopathy?
Steroids - most common
Statins
Heroin/Ecstasy = acute necrotizing myopathy
What is motor neuron disease?
Progressive disease
Widespread degeneration of motor neurons
Upper and lower motor neuron signs - wasting, spasticity, brisk reflexes
