NMD Part 2 Flashcards
what are muscular dystrophies
group of hereditary ms dz that weaken (primarily) skeletal ms of body
what are muscular dystrophies characterized by (3)
- progressive skeletal ms weakness
- defects in ms proteins
- death of ms cells & tissue
what is the prevalence of muscular dystrophies in childhood
comprises largest and most common group of inherited progressive neuromuscular disorders of childhood
what is the genetic inheritance of duchenne muscular dystrophy
x-linked recessive
what is the typical onset of duchenne muscular dystrophy
1-5yo
what is the course of the dz for duchenne muscular dystrophy
rapidly progressive
loss of walking typically by 9-10yo
death in late teens
what are 3 primary s/sx of muscular dystrophies
- insidious onset of ms weakness
- ms fatigue
- exercise intolerance
what are 5 secondary impairments of muscular dystrophies
- contractures
- postural malalignment, including scoliosis
- changes in appetite
- pain
- sleep apnea
what are 4 additional s/sx of muscular dystrophies
- ms cramping/pain
- ms twitching/fasciculations
- ms wasting (atrophy vs pseudohypertrophy)
- hypotonia
why does ms cramping occur in muscular dystrophies
contractile properties of these ms are changed and inefficient and ineffective
where will we expect to see contractures in muscular dystrophies and why
hip flexors & hamstrings
- if dec strength, sitting a lot
gastroc/PF
- lying in supine, gravity pushes into PF
what is the incidence of duchenne’s in males vs females
primarily in males bc linked to X
rare for females to manifest clinical sx
- if they do it’s very mild
what is the pathophysiology of DMD
mutation in dystrophin gene -> 1 or more exons (part of gene) are missing
what is the role of dystrophin in cells
mechanical stabilization of cell membrane
what does the mutation in the dystrophin gene result in
ms cell destruction d/t abnormal or missing dystrophin & its effect on the cell membrane
-> progressive loss of ms contractility d/t destruction of myofibrils
how many cases of DMD are new mutations
1/3
if the mom is a carrier of DMD, what is the risk for her son or her daughter of having DMD
son - 50% chance of inheriting DMD
daughter - 50% chance of being a carrier
- carrier may be mildly affected
what is the inheritance of BMD
x-linked recessive
BMD vs DMD in pathophys
BMD has same gene affected but some dystrophin is present
BMD course of dz compared to DMD
less severe and more slowly progressing than DMD
avg age of sx onset is later than DMD
amb longer (20s-30s) and longer lifespan than DMD
what is one clinical manifestation that is more common in BMD than DMD
cardiac myopathy
what are lab tests used to diagnose both DMD and BMD
CK values (high)
ms biopsies
- detect degen/regen of ms fibers, fibrosis, & fatty infiltrates
blood tests - detect mutation of dystrophin gene
why are blood tests a better option than ms biopsies
ms biopsies - damage ms that is already fragile
what is Gower’s sign
so weak that use hands to walk up legs to push up to stand and then stand up to lumbar lordosis
what is pseudohypertrophy
ms tissue replaced by adipose and collagen
- can create ms/joint contracture
what does neck flexor AG in DMD and BMD look like
significant head lag
what are 3 things that show up in a clinical exam to diagnose DMD and BMD
(+) Gower’s sign
calves - stiff, firm, pseudohypertrophy
motor difficulties - including neck flexor weakness
what is the criteria for ordering CK labs in the diagnostic guidelines for DMD
more than 3 sx over 2 or more categories (motor milestone delay, unusual gait, speech delay)
what are 3 ex of delayed motor milestones seen in DMD
- unable to walk by 18mo
- unable to jump by 2.5yo
- unable to run by 3yo
what are 3 ex of how unusual gait my present in DMD
- tiptoe walking
- frequent falling
- difficulty climbing steps
what are 3 ex of how speech delay may present in DMD
- no words spoken in first 18mo
- unable to speak sentences by 3yo
- any input from speech services (SALT)
what are 3 red flags identified in the diagnostic guidelines for DMD
- enlarged calf ms
- any ms pain/cramps
- any episodes of cola-colored urine
what can cola-colored urine indicate
rhabdomyolysis
what is a consideration with family planning and DMD
not unusual to have more than one boy w this condition in the family
- slower onset, could have another child by time dx the first
why is scoliosis seen in DMD and BMD
as lose trunk musculature, collapse into gravity
what are 3 medical interventions for DMD and BMD
no curative treatment
oral corticosteroids
anti-hypertensives
RNA therapy & exon-skipping
what are indications for oral corticosteroids in DMD and BMD (4)
prolong amb
reduce decline in CP function
reduce risk of scoliosis
improve life expectancy
what is the importance of oral corticosteroids in comparison to other medical interventions of DMD and BMD
SOC in early amb phase
what are 3 side effects of prednisone & defiazacort
- inc appetite and fluid retention
- behavior changes, irritability/outbursts, reduced attention
- reduced bone health - inc risk of fx
why are anti-hypertensives utilized in medical management of DMD and BMD
cardiomyopathy
- more common in BMD than DMD
what is the goal of RNA therapy & exon skippping
inc dystrophin levels
- > alter genetics to have DMD present more like BMD
amb and life expectancy prolonged
how does RNA therapy and exon skipping work
medication is exon specific
- fosters RNA replication to produce dystrophin
who is RNA therapy and exon skipping used in
pts w DMD w specific mutations
what are the preliminary results of RNA and exon skipping
inc dystrophin production
- effects on motor function TBD
what is the timeline progression of DMD in 5 steps
healthy bith
weakness noted 3-5yo
loss of amb by 9-12yo
- initiate use of light wt wc
power wc dependent 12-14yo
death 20-30yo
what is death caused by in DMD
cardiopulmonary complications
as weakness from DMD presents at ages 3-5yo, what are 4 other manifestations also seen
waddling gait
difficulty moving floor>stand
difficulty keeping up w friends
toe-walking
if you see a child w DMD toe-walking what is this likely telling you
gastroc is effected
what are 3 BSF impairments seen in ambulatory years of DMD/BMD
posture
ROM - progressive ms/joint contractures
strength
what does posture in DMD/BMD look like
calf pseudohypertrophy
- pushes them on toes and into lordosis
inc lumbar lordosis
- weak abdominals
scap winging
why are impairments in ROM seen in amb years in DMD/BMD
weakness & ms fibrosis