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BMS150 test 2 > skeletal muscle pathology (wk9) > Flashcards

skeletal muscle pathology (wk9) Flashcards

1
Q

what are muscular dystrophies

A

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

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2
Q

characteristic of muscular dystrophy

A

Characteristic muscle fiber necrosis and regeneration

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3
Q

which protein is effected in Duchenne muscular dystrophy

A

dystrophin; loss of function (deletion or frame shift)

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4
Q

is Duchenne x or y linked

A

x linked

  • Female carriers of the mutation can be mildly symptomatic due to unfavourable X- chromosome inactivation
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5
Q

what is the most common muscular dystrophy

A

Duchenne muscular dystrophy

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6
Q

what is the protein in Duchenne muscular dystrophy a key component of

A
  • Dystrophin is a key component of the dystrophin glycoprotein complex
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7
Q

what does the dystrophin glycoprotein complex do normally

A
  • This complex spans the plasma membrane, linking the cytoskeleton of the muscle fiber with the basement membrane.
  • As a result provides mechanical stability to
    the muscle fiber and it’s cell membrane (sarcolemma) during muscle contraction
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8
Q

what do defects in the dystrophin glycoprotein complex lead to

A

sarcolemma tears

§ Calcium influx from ECF àultimately triggering muscle fiber necrosis

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9
Q

what do sarcolemma tears allow for

A

Ca2+ influx –> necrosis

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10
Q

Duchenne pathogoloy

A

chronic muscle damage

muscle tissue replaced by collagen and fat cells

atrophy and hypertrophy of remaining muscle fibers

endomysial fibrosis

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11
Q

what is the sign/ test to do for duchenne

A

Gowers sign

  • (+) Gower’s sign: patient often have to push off the thighs in order to stand from sitting
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12
Q

clinical features of duchenne

A

delayed walking in kids

clumsy and unable to keep up with peers

week pelvic girdle muscles

pseudo hypertrophy of lower leg

cognitive impair + learning disability

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13
Q

age of wheel chair and death in duchenne?

A

9= wheelchair

§ Patients develop joint contractures, scoliosis, worsening respiratory
reserve and sleep hypoventilation
§ Development of cardiomyopathies and arrhythmias can occur in older patients due to impact of dystrophin in cardiac muscle

25-30= death

  • Commonlyfromrespiratoryinsufficiency,pulmonaryinfection, or heart failure
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14
Q

what is elevated in duchenne and then after decreases

A

creatine kinase

§ Initially high due to ongoing muscle damage

§ Levels decrease with loss of muscle mass

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15
Q

what protein is smaller and shorter in Becker muscular dystrophy

A

truncated dystrophin

so milder than duchennes

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16
Q

Becker vs duchenne

A

becker= truncated dystrophin
duchenne= absent dystrophin

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17
Q

is Becker x or y linked

A

x

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18
Q

onset and progression of Becker muscular dystrophy and life expectancy

A
  • Onset later in later childhood, adolescence, or adulthood
  • Generally similar but less severe than Duchenne Muscular dystrophy and has slower progression
  • Patients are still at risk of developing dilated cardiomyopathy, but this is very rare compared to Duchenne Muscular dystrophy
  • Prognosis:
    § Near-normal life expectancy
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19
Q

what is myotonia

A

sustained involuntary muscle contractions

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20
Q

what are the 2 types of triplet repeats in myotonic dystrophy

A

type 1: DMPK gene

type 2: CNBP gene

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21
Q

what type of genetic disorder is myotonic dystrophy

A
  • Autosomal dominant disorder caused by expansion of triplet repeats
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22
Q

type 1 vs type 2 of myotonic dystrophy

A
  • Type I: expansion of CGT trinucleotide repeat within the myotonic dystrophy protein kinase (DMPK) gene
  • Type II: CCTG repeat expansion within the gene nucleic acid- binding protein (CNBP) gene
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23
Q

type 1 vs type 2 myotonic dystrophy which affects voluntary vs involuntary

A

Both types affect voluntary muscles, type I also affects involuntary muscles

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24
Q

type 1 myotonic dystrophy pathogenesis SPARKNOTES

A

CLC1 chloride channel

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25
Q

Type 1 myotonic dystrophy pathogenesis

A

Skeletal muscle phenotype may result of “toxic” gain-of- function effect by CGT triplet repeat expansion within the DMPK that disrupts splicing of mRNA transcripts of other proteins, including the transcript of a chloride channel (CLC1)
§ Lack of CLC1 may explain myotonia

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26
Q

Type 2 myotonic dystrophy pathogenesis SPARKNOTES

A

zinc fingers

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27
Q

type 2 myotonic dystrophy pathogenesis

A
  • CNPB gene codes for a zinc-finger DNA binding protein
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28
Q

is type 1 or type 2 myotonic dystrophy more severe

A

type 1

29
Q

peripheral and facial VS proximal (hip and thigh) muscles

which is type 1 and which is type 2 myotonic distrophy

A

type1- peripheral and face (also involuntary muscles like GI and uterus)

type 2- proximal muscles

30
Q

type 2 myotonic dystrophy clinical features

A
  • Generally less severe with fewer extra-muscular symptoms
  • Tends to affect more proximal-located muscles (thigh and hip)
    § Often causing myalgic painm
31
Q

type 1 myotonic dystrophy clinical features

A
  • Myotonia, weakness, and wasting of peripheral muscles and
    facial muscles
    § Weakness of the hands, ptosis
  • Can also include: cardiomyopathy, intellectual disability, cataracts and endocrine disorders (abnormal glucose tolerance, male hypogonadism)
  • Patients with type I will also experience myotonia of involuntary muscles (eg. GI tract, uterus)
    § Dysphagia, constipation, uterine muscle abnormalities
32
Q

myotonic dystrophy diagnose and prognosis

A

via history and genetic testing

reduce life expectancy (54 years) due to respiratory and cardiac disease

33
Q

what is the most common drug related myopathy>

A

statin myopathy

34
Q

what causes a statin myopathy?

A

decreases cholesterol and depletion of CoQ10

  • Decreased cholesterol concentrations may impact sarcolemma
  • Depletion of Coq10 (Ubiquinone)
35
Q

clinical features of statin myopathy

A

weak muscles after exercise esp thighs

  • Myalgias and muscle weakness after exercise are the prominent clinical features; often severe enough to discontinue or switch medication
    § typically affects the thigh muscles
    § CoQ10 seems to help, may improve exercise tolerance
36
Q

which enzyme is blocked by statins in the cholesterol synthesis pathwya>

A

HMG CoA reductase (rate limiting step)

37
Q

myasthenia gravis is an autoimmune condition has autoantibodies against what?

A

acetylcholine receptors

aka post synaptic (nicotinic) receptors

38
Q

what is a thymoma (that can be seen in myasthenia gravis)

A

tumor of thyme epithelial cells

39
Q

what organ can the anti-act receptor autoantibodies in myasthenia gravis have an effect on?

A

thyme abnormalities (thymoma or thymic hyperplasia)

40
Q

who is myasthenia gravis most common in?

A
  • In young adults, it is more commonly found in females, in older adults in males.
41
Q

what causes the myofiber to not be able to response to Ach at the neuromuscular junction in Ab-Ach

A

§ Ab-Ach receptor complexes lead to a variety of problem ultimately limit the ability of the myofiber to respond to Ach at the neuromuscular junction:

  • Impact turnover of Ach receptors leading decrease in overall number of receptors
  • Blocks activation of the Ach receptors
  • Can damage the neuromuscular junction due to complement fixation
42
Q

2 initial findings of myasthenia gravis

A

ptosis and diplopia

43
Q

features of myasthenia gravis

A

proximal muscle weakness, worse with exercise

  • Fluctuating proximal muscle weakness
  • Ptosis and diplopia are common initial findings
    § Levator palpebrae, extraocular muscles often initially
    involved
    § In 15 – 25%, disease is exclusively extraocular
  • Proximal muscle involvement:
    § diaphragm, neck, facial muscles (snarling smile, difficulty
    chewing foods)
    § Dysphagia may develop to both solids and liquids
  • Usually worse with activity/ exercise and improves with rest (fatiguability)
  • Weakness seems to come and go initially (but eventually symptoms become more consistent)
44
Q

diagnosis of myasthenia gravis

A

+ antibody screen… and history, physical exam etcp

45
Q

what is myasthenic crisis RED FLAG

A

Respiratory weakness becomes severe enough to necessitate intubation

46
Q

prognosis of myasthenia gravis

A

Prognosis has improved significantly with current therapies
* Complicationscanincludepneumonia,falls,andmyastheniccrisis § Myasthenic crisis – RED FLAG
* Respiratoryweaknessbecomessevereenoughto necessitate intubation

47
Q

treat myasthenia gravis

A

Ach inhibitor drugs

§ Acetylcholinesterase inhibitors (first line of treatment) – increase half-life of Ach in the neuromuscular junction

§ Plasmapheresis & immunosuppressive drugs

§ Thymectomy for patients with a thymoma

48
Q

2 skeletal muscle tumors

A

mostly malignant

  • Rhabdomyosarcoma
  • Synovial Cell sarcoma
49
Q

Rhabdomyosarcoma; what are the 4 subtypes of this malignant mesenchymal tumor

A

4 subtypes: Alveolar, Embryonal, Pleomorphic, Spindle cell/sclerosis

50
Q

what is the malignant cell rhabodomyoblast rich in

A

myosin and actin

51
Q

where does Rhabdomyosarcoma occur most commonly

A

Alveolar and embryonal rhabdomyosarcoma are most common soft tissue sarcoma of childhood

52
Q

cause of Rhabdomyosarcoma

A

chromosomal tranlocations

53
Q

clinical features of Rhabdomyosarcoma

A
  • Tumour is detected as a mass, sometimes painful – metastases tend
    to cause respiratory difficulties, bone pain, and bone marrow failure * Tumours can occur anywhere in the body:
    § Head & neck, extremities, genitourinary tract
  • Embryonic type often tumours in mucosal cavities
    (bladder, vagina, nasopharynx, middle ear)
  • Alveolar type often results in tumours in the extremities
54
Q

prognosis of rhabdomyosarcoma

A
  • Tumours are aggressive, with a poor survival rate in older
    children/adults and those with metastatic disease
  • However, younger children with localized disease have a survival rate of about 80% 5 years after diagnosis
55
Q

synovial cell sarcoma is most common in?

A
  • Most common soft tissue tumour in adolescents and young adults
    (represents 5-10% of all soft tissue sarcomas)
56
Q

cause of synovial cell sarcoma

A

chromosomal translocation

57
Q

clinical features of synovial cell sarcoma

A

long-standing nodule, mass is often painless and deep around appendixes

  • Usuallyhistoryoflong-standingnodule
  • Present for years → increases rapidly in size over few months
  • Sometimes overlooked before growth
  • Tumor spreads along fascial planes - much more widespread than apparent on initial evaluation

§ Mass often is painless and deep
* Usually situated around knee, hands and feet
* Malignancy can affect any part of appendicular skeleton
* Distal extremity tumors have a better prognosis than proximal or truncal tumors

58
Q

what is fibromyalgia

A

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.

59
Q

who is most effected by fibromyalgia

A

young-adult to middle age females

60
Q

what is the classification of fibromyalgia

A

central sensitivity syndrome

neurosensory disorder characterized in abnormalities in pain processing by the CNS

61
Q

what is the scale for fibromyalgia diagnosis

A

Diagnosis is based on widespread pain index (WPI) and self-administered patient questionnaire

62
Q

what is the widespread pain index

A

for fibromyalgia –>pain or tender in 19 area

  • Widespread pain index – score of 0-19
  • Patients are asked if they have had pain or tenderness in 19 different body regions over the past week.
    § shoulder girdle, hip, jaw, upper arm, upper leg, lower arm, and lower leg on each side of the body, as well as upper back, lower back, chest, neck, and abdomen
    § Each region scores 1 point
  • Manual tender-points survey is also used during physical exam (though not required for diagnosis)

§ Self-administered patient questionnaire – score of 0-12 (section 2 & 3) * Section1:Assessdistributionofbodilypainasabove(scoreof0-
19; analogous to WPI)
* Section2:Assesesseverityofproblemswith:daytimefatigue, nonrestorative sleep, and cognitive dysfunction
§ Each is scored out from 0-3 (0=no problem, 3=severe problem)
* Section3:Assespainorcampsinlowerabdomen,depression,or headache in past 6 months
§ 1 point for each positive symptoms
* WPI/Section1iscombinedwithtotalpointsforsections2&3to
yield a score out of 0-31 (aka Polysymptomatic distress scale)

63
Q

what score in needed for widespread pain index for fibromyalgia and for how long to be diagnosed

A

> 13 score for 3+ months

A score of 13 or greater, with symptoms being present at similar level or severity for at least 3 months, and not explained by another disorder is diagnostic of fibromyalgia.

64
Q

what is chronic fatigue syndrome AKA

A

Myalgic encephalomyelitis (ME)

65
Q

what is chronic fatigue syndrome

A
  • Characterized by unexplained and profound fatigue that is
    worsened by exertion
  • Accompanied by cognitive dysfunction and impairment of daily functioning that persists for at least 6 months
66
Q

cause of chronic fatigue

A

viruses, envo triggers???

67
Q

who is chronic fatigue most common in

A

middle aged females

68
Q

what symptoms are needed to diagnose chronic fatigue syndrome

A
  • Presence of 3 or more of the following symptoms for at least 6 months and symptoms severity must be moderate or severe at least 50% of the time
  • Fatigue - unrelated to exertion and not relieved by rest
  • Post-exertional malaise (PEM)
  • Unrefreshing sleep – fatigue despite a night’s sleep

§ AND at least 1 of the following:
* Cognitive impairment
* Orthostatic intolerance

BMS150 test 2 (18 decks)

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