Muscle Diseases - Nelson

Question 1

Causes of Myopathy?

Answer 1

VINDICATE

V  ascular
I  nfection/inflammatory
N  eoplasm
D  egenerative
I  atrogenic
C  ongenital/hereditary
A  utoimmune
T  oxic/metabolic/trauma
E  ndocrine

Question 2

What is a great biomarker for muscle tissue injury?

Answer 2

Creatine KinaseCreatine kinase is released into the interstitial space and blood when cells are damaged.

Question 3

Relationship between CK-MM and CK-MB?

Answer 3

Skeletal muscle primarily expresses CK-MM (98%) with very low levels of CK-MB; however, as skeletal muscle is damaged and regeneration occurs, skeletal muscle can exhibit increased CK-MB expression.

Question 4

What happens to the checkboard pattern of motor unit innervation when the neurons/axons degenerate?
(Neurogenic atrophy)

Answer 4

The checkboard pattern is lost as motor units are reinervated by neurons already in the area. Becomes more homogenous in some areas

Question 5

What do the myocytes, neurons, and axons look like in myopathy?

Answer 5

The neurons and nerve fibers are normal while the myocytes are actually small due to degeneration or regeneration.

Question 6

Cause of Duchenne/Becker’s Muscular Dystrophy?

Answer 6

Duchenne - No dystrophin

Becker’s - altered dystrophin

Question 7

What muscle disease would show ring fibers?

Answer 7

Myotonic Dystrophy

Most common adult muscular dystrophy

Question 8

What is malignant Hyperpyrexia? (hyperthermia)

Answer 8

is a rare clinical syndrome characterized by a marked hypermetabolic state triggered by certain inhalational anesthetics

• Can cause uncontrolled release of Ca from muscle
• Leads to tetany, incr. muscle metab, and excessive HEAT

Question 9

Clinical presentation of dermatomyositis?

Answer 9

Inflammatory disorder of skin and skeletal muscle

Rash that causes discoloration of upper eyelids with edema

Myalgia and muscle weakness

Treat with immunosuppression

Question 10

Clinical presentation of polymyositis?

Answer 10

Muscle inflammatory disorder

Myalgia and muscle weakness

Treat with immunosuppresssion

Question 11

Inclusion Body Myositis. Anything very indicative of this condition?

Answer 11

Well you can differentiate it from dermatomyositis and polymyositis because it begins in the distal muscles

Muscle biopsy will show rimmed vacuoles!

Don’t treat with immune suppression!

Question 12

What are a couple examples of toxic myopathies?

Answer 12

Myopathies secondary to exposure to endocrine hormones, drugs, or toxic agents.

Thyrotoxic myopathy: hyperthyroidism can cause muscle degeneration/necrosis with regeneration. Patients can get exophthalmic opthalmoplegia with swelling and enlargement of the ocular muscles. In hypothyroidism, patients may get muscle fiber atrophy.

Ethanol myopathy: binge drinking can produce an acute toxic syndrome of rhabdomyolysis, with rapid breakdown of skeletal muscle.

Drug-induced myopathies: steroids, whether associated with Cushings syndrome or therapeutic use, can produce muscle fiber atrophy, predominately of type 2 fibers. Choroquine, used for treatment of malaria, can produce a proximal myopathy. Statins, used to reduce cholesterol, can also produce myopathy.

Question 13

Symptoms and treatment of myasthenia gravis?

Answer 13

Autoimmune disease that attacked ACh receptors - causes muscle weakness

Treat with anticholinesterases to stop the breakdown of acetylcholine in the synapse

Question 14

What is the cause and symptoms of Lambert-Eaton Myasthenia Syndrome?

Answer 14

Autoantibodies directed against calcium channels

Causes muscle weakness