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Neurology > Muscular Dystrophy > Flashcards

Muscular Dystrophy Flashcards

1
Q

What is the defective gene in Muscular Dystrophy?

A

DMD gene on X Chromosome

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2
Q

What does the defective gene produce?

A
  • Dystrophin: protein found in sleketal muscle
  • component of glycoprotein complex, provides mechanical reinforcement to muscle– sheilds from degradation
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3
Q

What are the effects of dystrophin?

A
  • without dystrophin: glycoprotein complex digested by proteases -> initiates degration of muscle fibers -> muscle weakness
  • Less dystrophin = more severe phenotype
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4
Q

How can DMD be inherited?

A

Mutation is linked in recessive X linked gene
* mostly effects males
* is possible that its not in family history

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5
Q

When would diagnosis be suspected?

A
  • delayed motor milestone and family history of DMD
  • child is not walking by 16-18 months
  • gowers sign
  • toe walking
  • calf hypertrophy
  • increase in transaminases (ALT, AST)
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6
Q

How can we confirm a DMD diagnosis?

A
  • genetic testing
  • muscle biopsy- less common
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7
Q

What are the signs and symptoms of DMD?

A
  • Weakness: onset between 2-3 years, may be late walkers, slow/awkard run, affects lower extremeties first, gower’s sign, wheelchair usually required by age 12-13
  • Elevated creatine kinase and transaminases: before clinical symptoms of disease
  • growth delay: slower than normal in first years of life
  • cardiomyopathy: may cause arrhythmias later in course
  • orthopedic complications: fractures due to falls and treatments with glucocorticosteriods– scoliosis
  • cognitive and behavioral disorders: increased risk of autism, ADHD, OCD, anxiety
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8
Q

What are the signs and symptoms of BMD?

A
  • weakness: onset starts later than DMD, physical strength retained until age 16 and often in adulthood
  • elevated ck
  • cardiomyopathy
  • cognitive and behavioral disorders: not as common or severe as DMD
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9
Q

What does DMD & BMD mortality look like?

A
  • DMD: most die in late teens to 20s beacuse of respiratiory problems
  • BMD: can live beyond 30 years
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10
Q

What are the first line treatments for MD?

A

Glucocortico steroids
* start before physical decline

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11
Q

What are alternative treatments for DMD and BMD?

A
  • disease modifying therapies
  • not in guidelines
  • act on genetic basis of the disorder by increasing production of fucntional dystrophin
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12
Q

What is the goal for using glucocorticosteroids in MD?

A

Improve muscle strength

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13
Q

What are the five benefits of Glucocorticoids in MD?

A
  • improve motor function
  • improve pulmonary function
  • reduce scoliosis
  • delay loss of ambulation
  • delay progression of cardiomyopathy and improve survival
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14
Q

What are 10 adverse effects of glucocorticoids?

A
  1. weight gain
  2. growth suppression
  3. hirsutism- excessive hair growth
  4. delayed puberty
  5. behavioral changes
  6. bone fractures
  7. acne
  8. GI symptoms
  9. cataracts- a cloudy area in the lens of your eye
  10. cushing like apperance- “moon face”
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15
Q

What are the two common glucocorticoids used in MD?

A

prednisone and deflazacort

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16
Q

What is the starting dose for prednisone?

A

0.75 mg/kg/day

17
Q

What is the starting dose for deflazacort?

A

0.9 mg/kg/day

18
Q

What are the comparitive ADE’s for prednisone and deflazacort?

A
  • Prednisone: more weight gain
  • Deflazacort: more growth suppression
19
Q

What would a treatment plan look like for someone on glucocorticoids?

A
  • steroid continued indefintely unless intolerable ADEs occur or significant obesity
  • if intolerable ADEs: decreased dose by 25-33%, reasses in 2-3 months
  • avoid abrupt or rapid withdrawl
20
Q

What are the four exon skipping therapies?

A
  • eteplirsen
  • golodirsen
  • vitolarsen
  • caimersin
21
Q

What would indicate the need for a disease modifying therapy?

A
  • Treatment of patients with confirmed mutationof DMD gene
  • Is amenable to specific exon skipping
22
Q

What is the mode of action of disease modifying therapies?

A

bind to a specific exon of dystrophin pre-mRNA resulting in exclusion of the exon during mRNA processing
* production of an interanlly turncated dystrophin protein increased dystophin expression

23
Q

What are the differences between the disease modyfing therapies that would effect ones choice?

A
  • Golodirsen, vitolarsen, casimersen all have ADE of renal toxicity including potentially fatal glomerulonephritis
  • measure serum cystatin C, urine dipstick, and urine protein-to-creatine ration prior to starting therapy (may not be reliable measure of kidney function in DMD pt due to low skeletal muscle mass

Neurology (6 decks)

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