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Flashcards in Muscle Diseases - Nelson Deck (14)
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Causes of Myopathy?


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


What is a great biomarker for muscle tissue injury?

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


Relationship between CK-MM and CK-MB?

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.


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

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


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

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


Cause of Duchenne/Becker's Muscular Dystrophy?

Duchenne - No dystrophin

Becker's - altered dystrophin


What muscle disease would show ring fibers?

Myotonic Dystrophy

Most common adult muscular dystrophy


What is malignant Hyperpyrexia? (hyperthermia)

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


Clinical presentation of dermatomyositis?

Inflammatory disorder of skin and skeletal muscle

Rash that causes discoloration of upper eyelids with edema

Myalgia and muscle weakness

Treat with immunosuppression


Clinical presentation of polymyositis?

Muscle inflammatory disorder

Myalgia and muscle weakness

Treat with immunosuppresssion


Inclusion Body Myositis. Anything very indicative of this condition?

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!


What are a couple examples of toxic myopathies?

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.


Symptoms and treatment of myasthenia gravis?

Autoimmune disease that attacked ACh receptors - causes muscle weakness

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


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

Autoantibodies directed against calcium channels

Causes muscle weakness