MSK: 18.4-6: Skeletal Muscle, NMJ, STT

Question 1

What is dermatomyositis?

Answer 1

inflammation of the skin and skeletal muscle

Question 2

What pathology might be simultaneously occurring in dermatomyositis?

Answer 2

carcinoma, esp GI

Question 3

What are the s/s of dermatomyositis?

Answer 3

bilateral proximal weakness; purple rash of upper eyelids (heliotrope rash); malar rash; red papules on the elbows, knuckles, and knees (Grotton lesions)

Question 4

How does proximal muscle weakness present?

Answer 4

can’t comb hair, can’t climb stairs

Question 5

What are the lab findings in dermatomyositis?

Answer 5

increased creatinine kinase, positive ANA and anti-Jo-1 Ab, perimysial inflammation of CD4+ cells with perifasicular atrophy

Question 6

What is the tx for dermatomyositis?

Answer 6

corticosteroids

Question 7

Perimysial inflammation of muscles = ?

Answer 7

dermatomyositis

Question 8

What is polymyositis?

Answer 8

an inflammatory disorder of skeletal muscle WITH NO SKIN INVOLVEMENT

Question 9

What causes polymyositis?

Answer 9

endomysial inflammation (CD8+ T cells) with necrotic muscle fibers

Question 10

Endomysial inflammation of muscles = ?

Answer 10

polymyositis

Question 11

What is the inheritance of muscular dystrophy?

Answer 11

X-linked

Question 12

What happens to the skeletal muscle in Muscular Dystrophy?

Answer 12

it’s replaced by adipose

Question 13

What is the cause of Duchenne Muscular Dystrophy?

Answer 13

deletions of dystrophin (Duchenne’s = deletions)

Question 14

What is the function of dystrophin?

Answer 14

an anchor molecule that anchors the ECM to skeletal muscles

Question 15

What is one lab finding in Muscular Dystrophy?

Answer 15

elevated creatinine kinase (damage to muscle cells)

Question 16

What is the problem in Becker Muscular Dystrophy?

Answer 16

MUTATED dystrophin (not deleted)

Question 17

How does Myasthenia Gravis occur?

Answer 17

an antibody competes for post-synaptic ACh receptors

Question 18

Weakness with increased use of the muscle occurs in ____, but this improves with rest.

Answer 18

Myasthenia Gravis

Question 19

Anticholinesterase agents ____ Myasthenia Gravis symptoms.

Answer 19

improve

Question 20

What are the initial s/s of Myasthenia Gravis?

Answer 20

drooping eyelids (ptosis) and diplopia

Question 21

Myasthenia Gravis is associated with what other pathology?

Answer 21

thymic hyperplasia or thymoma

Question 22

What is Lambert-Eaton Syndrome?

Answer 22

Abs against the pre-synaptic Ca++ at the NMJ

Question 23

What often causes Lambert-Eaton Syndrome?

Answer 23

small cell carcinoma (a paraneoplastic syndrome)

Question 24

What muscles are involved in Lambert-Eaton Syndrome?

Answer 24

proximal muscles; spares eyes

Question 25

What do anticholinesterase agents do in Lambert-Eaton Syndrome?

Answer 25

nothing

Question 26

In Lambert-Eaton Syndrome, muscle weakness ____ with use.

Answer 26

improves

Question 27

What is the tx for Lambert-Eaton Syndrome?

Answer 27

resection of the cancer

Question 28

What is the characteristic cell of a liposarcoma?

Answer 28

lipoblasts

Question 29

Cardiac rhabdomyoma are associated with _____.

Answer 29

tuberous sclerosis

Question 30

What is the characteristic cell of rhabdomyoscarcomas? What does it stain positively for?

Answer 30

rhabdomyoblast; desmin positive

Question 31

What is the most common site for a rhabdomyoscarcoma? What about in a young girl?

Answer 31

head and neck; young girl = vagina