AWABS - Myopathies

Question 1

Classification of myopathies

Answer 1

Primary
Secondary

Question 2

Primary myopathies

Answer 2

Muscular (muscular dystrophy)
Congenital
Metabolic

Question 3

Acquired myopathies

Answer 3

Metabolic and endocrine
Dermato- and poly- myositis
Drug induced
Infectious
?Polymyalgia ?Fibromyalgia

Question 4

Metabolic myopathies

Answer 4

Glycogen storage
Lipid storage

Question 5

Muscular dystrophy features

Answer 5

Involves dystrophin
Inherited
Progressive

Question 6

Muscular dystrophy synptoms

Answer 6

Inability to regenerate
Proximal weakness
Respiratory involvement eventually
Myotonia

Question 7

Types of muscular dystrophy

Answer 7

Dystrophia myotonica
Becker’s
Thomsen’s
Duschenne’s muscular / myotonic dystrophy

Question 8

Congenital myopathy features

Answer 8

Rare
Genetic defects lead to protein defects
Non progressive
Reduced contractile ability

Question 9

Metabolic myopathy features

Answer 9

Hereditary enzyme defects
Errors in metabolism of ATP

Question 10

Examples of glycogen storage diseases

Answer 10

Pompe’s disease
McArdle’s disease

Question 11

Enzyme affected in Pompe’s disease

Answer 11

Acid maltase

Question 12

Enzyme affected in McArdle disease

Answer 12

Myophosphorylase

Question 13

Examples of lipid storage diseases

Answer 13

Carnitine palmitoyltransferase deficiency
Myopathic carnitine deficiency

Question 14

Examples of acquired metabolic and endocrine myopathies

Answer 14

Thyroid disease
Parathyroid disease
Pituitary disease eg Addison’s
Corticosteroids eg Cushing’s
Diabetes

Question 15

Acquired infectious causes of myopathy

Answer 15

Trichinosis
Toxoplasmosis
HIV
Coxsackie
Lyme disease
Influenza

Question 16

Acquired drug induced causes of myopathy

Answer 16

Statins
Steroids
Alcohol
Cocaine
Colchicine

Question 17

Most common form of myopathy

Answer 17

Drug induced

Question 18

Incidence of Duchenne’s muscular dystrophy

Answer 18

1:4000 in boys

Question 19

Features of Duchenne’s

Answer 19

Progressive muscular wasting
Poor balance
Drooping eyelids
Atrophy
Scoliosis
Waddling gait
Cardiomyopathy

Question 20

Genetics of Duchenne’s

Answer 20

X linked recessive

Mutation on dystrophin gene at locus Xp21

Question 21

Ix for Duchenne’s

Answer 21

Raised CK
EMG
Genetic testing
Muscle biopsy

Question 22

Rx of Duchenne’s

Answer 22

High dose steroids
Ataluren
Exercise / Physio

Question 23

Role of steroids in Duchenne’s

Answer 23

Increase muscle strength
Reduce Symptoms
Prolong life

Question 24

Dystrophin features

Answer 24

Large cytosolic protein
Hydrophobic
Rod shaped
Connects cytoskeleton to extracellular matrix

Question 25

Becker's dystrophy genetics

Answer 25

Same as Duchenne's

Question 26

Features of Becker's

Answer 26

More rare than Duchenne's Later onset (teens) Milder Normal life expectancy Dilated cardiomyopathy

Question 27

Features of dystrophia myotonica (myotonic dystrophy)

Answer 27

Inherited Slow progressing Difficulty initiating movement Cataracts Cardiac conduction defects

Question 28

Categories of Dystrophia myotonica

Answer 28

DM1 DM2

Question 29

Features of DM1

Answer 29

Steinert disease Severe congenital Childhood

Question 30

Features of DM2

Answer 30

Proximal myotonic myopathy Adult onset Rare

Question 31

Genetics of dystrophia myotonica

Answer 31

Autosomal dominant

Question 32

Features of acid maltase deficiency

Answer 32

Resp failure Pulmonary HTN Cardiomegaly Aspiration risk

Question 33

Lipid storage myopathy features

Answer 33

Hypoglycaemia Acidosis Rhabdomyolysis Cardiac failure

Question 34

Management of lipid storage myopathies in perioperative period

Answer 34

Require administration of supportive substrates

Question 35

Implication of mitochondrial myopathies for anaesthetics

Answer 35

Worsened by depressant anaesthetics Maintain normoglycaemia Avoid suxamethonium Sensitive to non depolarising NMB so give 10-20% dose Risk of heart block and seizures Risk of rhabdo with volatiles - ?use TIVA

Question 36

Features of peripheral neuropathy to distinguish from myopathy

Answer 36

Distal muscles affected Fasciculations Somatosensory abnormalities Reduced reflexes