Peripheral Nerve Disorders II - Exam 4 Flashcards
(129 cards)
What is the etiology of muscular dystrophy? How does a pt get muscular dystrophy?
Complex set of INHERITED myopathic disorders.
inherited: X linked recessive!!
Muscular dystrophy presents as ________ WITHOUT _______ often ______. What lab value will be elevated?
muscle weakness and wasting
WITHOUT sensory loss
progressive
elevated CK
What are the 2 types of MD that we learned about in lecture? Which one is worse? What percentage of all MD?
Duchenne MD** worse: 23%
Becker MD: 10%
What groups of muscles are commonly affected in both Duchenne and Becker MD?
shoulders, forearms and thighs
How does Duchenne MD compare to Becker MD? include protein _____
Duchenne is more severe s/s
-dystrophin (protein) is markedly reduced or absent
Becker: similar to DMD but later onset and milder course
-dystrophin levels are normal, but protein is qualitatively altered (misshapen)
In MD the genetic defect is located on the _______. What is it? What does it code for?
short arm of X chromosome
dystrophin: (protein): helps anchor the outside of the muscle cell to the inside of the muscle cell. plays a huge role in strength of muscle
Can DMD be recognized in early pregnancy?
YES! can be recognized in early pregnancy in about 95% of women
What is the trend with regards to MD as a pts ages?
older the pt gets the higher likely they are to die, survival rates into adulthood is not great
58% of males 20-24
How does Duchenne MD typically present?
weakness usually around 2-3 years old
starts proximal and moves distal, weakness is progressive
Gower’s sign
What is Gower’s sign? What disease is it commonly seen with?
using hands to push up to stand, shows progressive muscle weakness
MD
Besides weakness, name additional s/s of Duchenne MD.
What are the 4 typical comorbidities associated with Duchenne MD?
primary dilated cardiomyopathy: MITRAL regurg. can lead to heart failure and arrhythmias in later stages
fractures
progressive scoliosis
impaired pulmonary function due to respiratory muscle weakness
______ is the clinical distinction between Becker and Duchanne MD. How long can they remain _______? ______ is usually worse when compared to Duchanne
retained strength
Usually ambulatory at least until age 15 and commonly into adult life
WORSE: cardiac dz in Becker due to retained ability to exercise
As a PCP, what 3 tests should you order if you suspect MD? Then what should you do?
serum CK
EKG
EMG
refer to neuromuscular specialist/ MD center
What will the serum CK show in a pt with MD? When is it at its peak? Is CK elevated or decreased in carriers?
elevated in DBMD patients prior to clinical signs of disease
Peaks ~age 2; usually 5-10x ULN or more; then falls by 25% per yr
CK increased up to 10x ULN in carriers - 50% DMD carriers, 30% BMD carriers
What will the EKG show in a pt with MD? What will the EMG show?
tall right precordial R waves, increased R/S ratio, deep Q waves in I, aVL, V5-6
DMD also associated with conduction disturbances leading to variety of arrhythmias
EMG: myopathic changes
_____ is the first line and confirms dx test in MD
Genetic analysis
What will a muscle bx show in a pt with MD? What about dystrophin specifically? Give DMD and BMD results
degeneration, regeneration, isolated “opaque” hypertrophic fibers, replacement of muscle by fat and connective tissue
DMD - most pts have total or near-total absence of dystrophin
BMD - ~85% with abnormal size and amount; ~15% with normal size, abnormal amount
______ is the mainstay of tx for MD. When is it recommended to start? What age? What are the dosing considerations?
Glucocorticoids (prednisone)
start before significant physical decline occurs
boys 4+ years old whose motor skills have plateaued or starting to decline
do NOT abruptly stop, need to taper and may need stress dosing
What are 3 good parameters to assess benefits of glucocorticoids in MD?
Timed muscle function tests
pulmonary function tests
age at loss of independent ambulation
________ : systemic glucocorticoid specifically for DMD. What is potential SE? More or less SE when compared to prednisone?
Deflazacort (Emflaza)
may stunt growth
LESS general SE when compared to prednisone
________ is the newest glucocorticoid option for MD but it is expensive
Vamorolone (Agamree)
________ binds to exon 51 of mRNA, causes skipping of exon 51 in translation of the DMD gene. What percent of DMD pts have this variant? What is the theoretical end result?
Eteplirsen (Exondys 51)
13% of DMD pts have exon-51 variants
increases dystrophin
______ and ________ Causes skipping of exon 53 in translation of the DMD gene. What percent of DMD pts have this variant?
Golodirsen (Vyondys 53) and Vitolarsen (Viltespo)
8% of DMD pts have exon-53 variants