Exam 5 muscular diseases

Question 1

Define muscular dystrophy

Answer 1

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

Question 2

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

Answer 2

True; Duchenne’s MD, Becker MD

Question 3

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

Answer 3

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

Question 4

What is the difference between Duchenne and Becker MD?

Answer 4

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

Question 5

What are the two classical movement signs of DMD?

Answer 5

waddling “duck-like” gait, place hands on knees to assist standing (Gower’s maneuver)

Question 6

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

Answer 6

enlargement of calf due to replacement with adipose tissue

Question 7

What is the blood marker of DMD pts?

Answer 7

elevated creatine kinase early in disease

Question 8

What is the progression of DMD?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

What is the treatment of BMD?

Answer 10

immunosuppression

Question 11

What can female carriers of BMD be at risk for?

Answer 11

cardiomyopathy, will show increased creatine kinase

Question 12

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

Answer 12

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

Question 13

What is incorrect in myotonic dystrophy?

Answer 13

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

Question 14

What do patients with myotonic dystrophy present with?

Answer 14

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

Question 15

What does a muscle biopsy of myotonic dystrophy look like?

Answer 15

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

Question 16

What are the three subgroups of inflammatory myopathies?

Answer 16

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

Question 17

What is dermatomyositis?

Answer 17

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

Question 18

What is the molecular/immunological basis of dermatomyositis?

Answer 18

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

Question 19

What are the classical clinical presentations of dermatomyositis?

Answer 19

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)

Question 20

What are the lab values of dermatomyositis?

Answer 20

increased creatine kinase, treat w/ immunosuppressives

Question 21

What does difference between polymyositis and dermatomyositis?

Answer 21

polymyositis has a lack of skin or vascular injury involvement

Question 22

What is the pathogenesis of polymyositis?

Answer 22

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

Question 23

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

Answer 23

Inclusion body myositis begins to affect distal muscles first

Question 24

Do immunosuppressive agents help treat inclusion body myositis?

Answer 24

nope

Question 25

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

Answer 25

Statins

Question 26

What is the cause of the symptoms of myasthenia gravis?

Answer 26

Antibodies against the nicotinic receptor at neuromuscular jxn

Question 27

What are ways to diagnose myasthenia gravis?

Answer 27

detecting autoantibodies to nicotinic receptor, edrophonium test

Question 28

What is the treatment of myasthenia gravis?

Answer 28

anti cholinesterase drugs (neostigmine, pyridostigmine, edrophonium)

Question 29

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

Answer 29

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

Question 30

What causes Lambert-Eaton myasthenia syndrome?

Answer 30

autoantibodies against presynaptic calcium channels that blocks acetylcholine release

Question 31

What are the three isotypes of creatine kinase?

Answer 31

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

Question 32

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

Answer 32

CK-MM; switches to CK-MB

Question 33

What kinds of diseases is elevated creatine kinase seen in?

Answer 33

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

Question 34

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

Answer 34

cardiac troponin 1

Question 35

What does myoglobinemia occur?

Answer 35

When cardiac or skeletal muscle is damaged

Question 36

What can myoglobinuria cause?

Answer 36

rhabdomyolysis (acute tubular necrosis with acute renal failure)