Pathology - Skeletal Muscle Pathology

Question 1

Group of inherited muscle disorders leading to progressive weakness and muscle wasting

Answer 1

Muscular dystrophies

Question 2

What are characteristics of muscular dystrophies?

Answer 2

Muscle fiber necrosis and regeneration

Question 3

Most common muscular dystrophy?

Answer 3

Duchenne muscular dystrophy

Question 4

Duchenne MD Etiology?

Answer 4

• X-linked
• LOF of dystrophin

Question 5

Deletion or frameshift mutations result in ______ of dystrophin

Answer 5

total absence

Question 6

What is dystrophin a key component of?

Answer 6

Dystrophin glycoprotein complex

Question 7

What does the dystrophin glycoprotein complex do?

Answer 7

spans the plasma membrane - linking the cytoskeleton of the muscle fiber with the basement membrane

Question 8

Defects in dystrophin glycoprotein complex leads to what?

Answer 8

Sarcolemma tears = ca influx from ECF = necrosis of muscle fibers

Question 9

As Duchennes MD progresses, what replaces muscle tissue?

Answer 9

Collagen and fat cells

Question 10

What is (+) Gower’s sign?

Answer 10

Patient has to push off of thighs in order to stand up

Question 11

Where does weakness begin in Duchenne MD?

Answer 11

Pelvic girdle muscles and shoulder girdle

Question 12

What can develop in older patients with Duchenne MD?

Answer 12

Cardiomyopathies and arrythmias

Question 13

Duchenne diagnosis?

Answer 13

• Progressive loss of creatine kinase
• Genetic testing (definitive)
• Muscle biopsies

Question 14

Etiology of Becker MD?

Answer 14

• X-linked
• Truncated dystrophin due to mutation

Question 15

Difference between Duchenne and Becker MD?

Answer 15

No dystrophin function in Duchenne, but partial function in Becker

Question 16

definition of myotonia?

Answer 16

sustained involuntary muscle contraction

Question 17

Inheritance pattern of myotonic dystrophy?

Answer 17

Autosomal dominant disorder caused by expansion of triplet repeats

Question 18

Type I Myotonic Dystrophy?

Answer 18

Expansion of CGT tri-nt repeat in DMPK gene

Question 19

Type II Myotonic Dystrophy?

Answer 19

CCTG repeat expansion in CNPB gene

Question 20

Type I Myotonic Dystrophy Pathogenesis?

Answer 20

Toxic gain of function = disrupted splicing of mRNA transcript of other proteins, including transcript of chloride channel

Question 21

Type II Myotonic Dystrophy Pahtogenesis?

Answer 21

CNPB gene codes for a zinc-finger binding domain

Question 22

Is type I or type II myotonic dystrophy more sever?

Answer 22

type I more severe

Question 23

Patients with type I will also experience myotonia of what?

Answer 23

Involuntary muscles

Question 24

Where does type II myotonic dystrophy tend to affect?

Answer 24

Proximally located muscles (thigh or hip)

Question 25

Most-common drug-related myopathy?

Answer 25

Statin myopathies

Question 26

Pathophysiology of statin myopathies?

Answer 26

- decreased cholesterol may impact sarcolemma - depletion of CoQ10

Question 27

Enzyme blocked by statins?

Answer 27

HMG-CoA reductase

Question 28

Autoimmune condition associated with autoantibodies directed against acetylcholine receptors?

Answer 28

Myasthenia Gravis

Question 29

There is a strong association between anti-Ach receptor autoantibodies and _____ abnormalities

Answer 29

thymic

Question 30

What does the limit of the ability of the myofiber to respond to Ach at the neuromuscular junction do?

Answer 30

- impact turnover of Ach receptors - Blocks activation of Ach receptors - Damage neuromuscular junction

Question 31

Common initial findings of MG?

Answer 31

Ptosis and diploplia

Question 32

Redflag of MG?

Answer 32

Myasthenic crisis = Respiratory weakness becomes severe enough to necessitate intubation

Question 33

Nearly all skeletal muscle tumors are _______

Answer 33

Malignant

Question 34

Malignant mesenchymal tumour with skeletal muscle differentiation

Answer 34

Rhabdomyosarcoma

Question 35

4 subtypes of Rhabdomyosarcoma?

Answer 35

Alveolar, Embryonal, Pleomorphic, spindle cell

Question 36

Most common soft tissue sarcoma of childhood?

Answer 36

Alveolar and embryonal rhabdomyosarcoma

Question 37

Most common soft tissue tumour in adolescents and young adults?

Answer 37

Synovial cell sarcoma

Question 38

Syndrome of persistent widespread pain, stiffness, fatigue, disrupted sleep, and cognitive difficulties. It is often accompanied by anxiety/depression and impairment of activities of daily living

Answer 38

Fibromyalgia

Question 39

Who is fibromyalgia most common in?

Answer 39

Young-adult to middle-aged females

Question 40

What type of disorder is fibromyalgia considered?

Answer 40

Neurosensory disorder characterized in abnormalities in pain processing by the CNS

Question 41

Fibromyalgia diagnosis?

Answer 41

WPI and self-administered patient questionnaire

Question 42

Unexplained and profound fatigue that is worsened by exertion

Answer 42

Chronic Fatigue Syndrome

Question 43

Who is mainly affected by chronic fatigue syndrome?

Answer 43

Young to middle-aged adult females

Question 44

Diagnostic criteria for chronic fatigue syndrome?

Answer 44

- Fatigue - unrelated to exertion and not relieved by rest - Post-exertional malaise (PEM) - Unrefreshing sleep – fatigue despite a night’s sleep + either cognitive impairment and/or orthostatic intolerance