Diseases of Muscle

Question 1

What are the symptoms of muscle diseases?

Answer 1

Wasting 
Pain
Cramping
Fasiculations
Weakness

Question 2

What investigations are used to diagnose muscle diseases?

Answer 2

Clinical neurological examination
Electromyography - records electrical activity in muscles
Nerve conduction studies - tests peripheral nerves
MRI
Serum/Bloods- antibodies

Question 3

What are the 3 different origins for muscle disease?

Answer 3

Neurogenic muscle disease - brain problems
Motor end-plate disorders e.g. myasthenia gravis
Primary muscle (myopathies) - destructive/non destructive

Question 4

Where is a biopsy for suspected muscle disease usually taken from?

Answer 4

Quadriceps

Needle/core sample removed

Question 5

Muscular dystrophies are normally due to a lack of which protein?

Answer 5

Sarcolemma

Question 6

Duchenne muscular dystrophy and limb girdle muscular dystrophy are diseases of what?

Answer 6

the plasma membrane

Question 7

Duchenne Muscular Dystrophy has what kind of inheritance?

Answer 7

Sex linked

Recessive

Question 8

What protein is lacking in Duchenne Muscular Dystrophy?

Answer 8

dystrophin

Question 9

How does Duchenne Muscular Dystrophy present (inc histologically)?

Answer 9

Progressive proximal wasting of muscles
Hypertrophy of calves
Loss of muscle mass
Fibers hypertrophy due to muscle loss 
Immature fibers 
Fibrosis

Question 10

Emery-Dreifuss Muscular Dystrophy has what kind of inheritance?

Answer 10

X linked recessive

Question 11

How does Emert-Dreifuss Muscular Dystrophy normally present?

Answer 11

Weakness of proximal arm and distil leg
Early contractures
Cardiomyopathy

Question 12

What 2 conditions is limb girdle muscular dystrophy similar to and needs to be excluded from?

Answer 12

Spinal muscular atrophy

Bone mineral density

Question 13

Core diseases and nemaline myopathies come under dysfunction to what protiens?

Answer 13

Myofibrillar and internal cytoskeletal proteins

Question 14

Core diseases have what kind of inheritance?

Answer 14

Dominant

Question 15

The central core is where and only occurs in which type of fibre?

Answer 15

Zone in the center of a muscle fiber

Type I

Question 16

How does central core disease present histologically?

Answer 16

Variation is fibre size
Every fibre contains 1 or more cores
No mitochrondia

Question 17

How does Nemaline myopathy present? (inc histologically)

Answer 17

Generalised neonatal hypotonia - low muscle tone
Respiratory insufficiency
High arched palate
Kyphoscoliosis 
Abnormal Z band with rod bodies attached

Question 18

How is Nemaline myopathy inherited?

Answer 18

Autosomal recessive

Question 19

Malignant hyperthermia is what type of defect?

Answer 19

Ion channel and ion transporter defect

Question 20

What is malignant hyperthermia?

Answer 20

Abnormal susceptibility to certain anesthetic agents

Prolonged rise in intracellular Ca - rigid contractions/elevation in body temp

Question 21

How does malignant hyperthermia present histologically?

Answer 21

moderate increase in central nuclei

Occasional fibers contain cores

Question 22

Myotonic dystrophies and facioscapulohumeral dystrophy are defects of what?

Answer 22

Myopathies based on complex molecular defects
Myotonic dystrophies = repeat expansion diseases
Facioscapulohumeral dystrophy = large telomeric deletion disease

Question 23

How is myotonic dystrophy inherited?

Answer 23

Dominantly

Question 24

How does myotonic dystrophy present symptomatically?

Answer 24

Myotonic and progressive weakness of facial muscles - long face
Cardaic conduction defects

Question 25

How does myotonic dystrophy present histologically?

Answer 25

``` Atropy of type I fibres Type II hypertrophy Central nuclei Moth eaten and targetoid fibres Ring fibres ```

Question 26

How is Facioscapulohumeral dystrophy inherited?

Answer 26

Dominantly

Question 27

How does Facioscapulohumeral dystrophy present?

Answer 27

``` Facial/shoulder muscle weakness Assymetrical weakness Affects myocardium Progressive deafness Retinal vasculopathy ```

Question 28

What is myasthenia gravis?

Answer 28

Autoimmune disease | IgG antibodies against Ach receptors

Question 29

What is Eaton-Lambert Myasthenic syndrome?

Answer 29

Autoimmune | Antibodies against Ca voltage gated ion channels

Question 30

How do mitochondrial myopathies present histologically?

Answer 30

Ragged red fibres | Accumulation of lipid

Question 31

Dermatomyositis is what type of myopathy?

Answer 31

Immune and infectious myopathies

Question 32

What is Dermatomyositis and how does is present?

Answer 32

``` Inflammation of the skin and underlying muscle tissue Autoimmune/cancer Scaly rash Discoloration Swelling ```

Question 33

How does Dermatomyositis present histologically?

Answer 33

Mononuclear cells infiltrate the muscle - fiber necrosis/fibrosis Inflammation where B cell predominant

Question 34

What are the most common drugs that induce a myopathy?

Answer 34

Steroids - most common Statins Heroin/Ecstasy = acute necrotizing myopathy

Question 35

What is motor neuron disease?

Answer 35

Progressive disease Widespread degeneration of motor neurons Upper and lower motor neuron signs - wasting, spasticity, brisk reflexes