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Flashcards in Exam 5 muscular diseases Deck (36):
1

Define muscular dystrophy

heterogenous group that results in muscle weakness and eventually muscle atrophy and wasting, muscle is replaced with fibrofatty tissue

2

T/F: most common muscular dystrophies are X-linked?

True; Duchenne's MD, Becker MD

3

What is the gene that is deficient/mutated in muscular dystrophy? What does it do?

dystrophin; located adjacent to sarcolemma and forms interface between intracellular contractile units and extracellular connective tissue

4

What is the difference between Duchenne and Becker MD?

DMD have littler or no dystrophin, Becker have decreased amount of defective dystrophin

5

What are the two classical movement signs of DMD?

waddling "duck-like" gait, place hands on knees to assist standing (Gower's maneuver)

6

What is pseudo hypertrophy? Where does it usually occur in DMD pts?

enlargement of calf due to replacement with adipose tissue

7

What is the blood marker of DMD pts?

elevated creatine kinase early in disease

8

What is the progression of DMD?

Develop symptoms by age 5, weakness in pelvic girdle, followed by shoulder girdle

9

What does a muscle biopsy of Becker's MD and DMD show?

shows variation of muscle fiber size, increased endomysial connective tissue, degeneration of muscle fibers, replacement of muscle with fat and connective tissue

10

What is the treatment of BMD?

immunosuppression

11

What can female carriers of BMD be at risk for?

cardiomyopathy, will show increased creatine kinase

12

What is the genetic difference of myotonic dystrophy and DMD/BMD?

Myotonic is an autosomal dominant disorder, where as DMD/BMD are X-linked

13

What is incorrect in myotonic dystrophy?

increased CTG trinucleotide repeat sequences on chromosome 19, which affects mRNA for dystrophia myotonia protein kinase. Affects chloride channels

14

What do patients with myotonic dystrophy present with?

abnormal gait, weakness of hand and wrist, facial muscle atrophy/sagging face, ptosis (drooping eye) and open mouth

15

What does a muscle biopsy of myotonic dystrophy look like?

selective atrophy of type 1 fibers as well as ring fibers; elevated creatine kinase

16

What are the three subgroups of inflammatory myopathies?

Infection (group A strep, clostridial gas gangrene), Systemic inflammatory disease (SLE), Non-infectious inflammatory diseases (dermatomyositis)

17

What is dermatomyositis?

autoimmune against small blood vessels and capillaries in skeletal muscle; characteristic skin rash

18

What is the molecular/immunological basis of dermatomyositis?

activated B and T cells and antibodies with complement activation causing capillary damage

19

What are the classical clinical presentations of dermatomyositis?

Classic rash is violaceous discoloration of upper eyelids associated with periorbital edema, accompanied by scaling erythematous eruption or dusky red patches over joints (Gorton papule)

20

What are the lab values of dermatomyositis?

increased creatine kinase, treat w/ immunosuppressives

21

What does difference between polymyositis and dermatomyositis?

polymyositis has a lack of skin or vascular injury involvement

22

What is the pathogenesis of polymyositis?

caused by immunological injury to muscle by activated CD8+ T cells; muscle biopsy shows lymphatic inflammation surrounding and invading muscle fibers

23

What is the difference in terms of affects between dermatomyositis and polymyositis, and inclusion body myositis

Inclusion body myositis begins to affect distal muscles first

24

Do immunosuppressive agents help treat inclusion body myositis?

nope

25

What is the most common cause of drug-induced myopathies?

Statins

26

What is the cause of the symptoms of myasthenia gravis?

Antibodies against the nicotinic receptor at neuromuscular jxn

27

What are ways to diagnose myasthenia gravis?

detecting autoantibodies to nicotinic receptor, edrophonium test

28

What is the treatment of myasthenia gravis?

anti cholinesterase drugs (neostigmine, pyridostigmine, edrophonium)

29

What is the classical sign of Lambert-eaton myasthenia syndrome?

rapid repetitive stimulation of the affected muscle increases the muscle response; pts usually respond with extremity weakness

30

What causes Lambert-Eaton myasthenia syndrome?

autoantibodies against presynaptic calcium channels that blocks acetylcholine release

31

What are the three isotypes of creatine kinase?

CK-BB, CK-MB, CK-MM (B= brain, M= muscle)

32

What isoform is most dominant in skeletal muscle? What does it switch to when it's damaged and is regenerating?

CK-MM; switches to CK-MB

33

What kinds of diseases is elevated creatine kinase seen in?

Skeletal muscle diseases such as inflammatory myopathies, muscular dystrophy, rhabdomyolysis, skeletal muscle trauma

34

What is the specific elevated blood protein seen after an MI?

cardiac troponin 1

35

What does myoglobinemia occur?

When cardiac or skeletal muscle is damaged

36

What can myoglobinuria cause?

rhabdomyolysis (acute tubular necrosis with acute renal failure)