Unit 5 Case 3: Duchenne Muscular Dystrophy Flashcards
pathogenesis of DMD
mutation in dystrophin gene leads to progressive muscle fiber degeneration and weakness
inherited from mother/ spontaneous mutation
mutation on short arm of X chromosome, more common in males
out of frame mutation leads to a non-functional protein
exon deletion
Xp21.2
muscles breaks down and replaced by fat
presents age 2-5
pathophysiology of DMD
dystrophic anchors muscle fiber and sarcolemma
links cytoskeleton to ECM
dystrophin geen associated protein complex, DAPC
stabiliser preventing contraction induced damage
every contraction: muscle becomes disorganised leading to damage, inflammation and myofbier necrosis
absence of dystrophin
reduces muscle stiffness
increases sarcolemma deformability
compromises mechanical stability of muscle fiber
definition of normal child development
expected pattern of physical, cognitive and emotional growth and change that occurs in children as they progress from infancy to adolescence
what factors affect childhood development
nutrition
environment
genetics
health
relationships
experiences
education
what are the 4 stages of normal child development
infancy
early childhood
middle childhood
adolescence
infancy
ages 0 to 2
basic motor skills such as crawling and walking
social skills such as smiling and eye contact
early childhood
2-6
language skills
form relationships with others
middle childhood
6-11
more advanced cognitive skills such as memory and problem solving
more independent
adolescence
11-18
significant physical emotional and cognitive changes as they prepare to transition into adulthood
presentation of DMD
proximal muscle weakness
progressive muscle weakness
motor delay
global developmental delay
flexion contracture
delayed speech or language development
cognitive impairment
cardiomyopathy
muscle hypertrophy of calf muscles
waddling gatit
specific learning disability
skeletal muscle atrophy
scoliosis
respiratory insufficiency
cardiomyopathy
myocardial disorder where heart is structurally and functionally abnormal
cognitive impairment
abnormal cognition with deficits in thinking, reasoning and remembering
flexion contracture
flexed joint
can’t be straightened actively or passively
chronic loss of joint motion due to structural changes in muscles, tendons, ligaments of skin
global developmental delays
delay in achievement of motor/mental milestones in domains of development as a child
describes children under the age of 5
Lordosis/ lordotic pressure
excessive curvature in lumbar portion of spine
swayback appearance
scoliosis
abnormal lateral curvature of the spine
symptoms aged 1-3
difficulty walking, running, jumping and climbing stairs
walking may include a waddle
pick child up they may sip through hands due to looseness of shoulder muscles
children walk on toes with feet apart to maintain balance
frequent falls
bulky but not strong calf muscles
Gower’s sign
developmental delay
contractures
progressive heart enlargement
respiratory function
serial monitoring should start aged 5-6
diaphragm may weaken
make coughing difficult, increasing risk of serious respiratory infection
get flu vaccines
simple cold may develop leading to pneumonia
anatomy relevance of dystrophin
responsible for connecting the cytoskeleton of each muscle fiber to underlying basal lamina
absence of dystrophin stops calcium entering the cell membrane
affects cell signalling
water enters mitochondria, causes the cell to burst
increased oxidative stress in the cell will damage the sarcolemma= cell death
muscle fibers undergo necrosis and are replaced by connective tissue
dystrophin also located in the hippocampus= non-progressive memory and social behavioural problems
what is Gower’s sign
testing for Gower’s sign
place patient in the supine position and ask them to rise
positive= inability to lift trunk without using hands and arms to brace and push, indicates a proximal weakness
from lying they will roll to kneeling position and push on the ground with extending forearms to lift hips and straighten legs= triangle with hips at apex and hands and feet on the floor to create a base
hands push on knees and lift trunk
complications of DMD
difficulty using arms
contractures
breathing difficulties
scoliosis
heart problems
swallowing problems/ dysphagia
difficulty walking
contractures as a complication of DMD
limit further mobility
can become severe and cause discomfort
postpone severity by doing ROM exercises
could have heel cord surgery to release tendon
breathing difficulties as a complication of DMD
loss of respiratory muscle strength
ineffective cough
decreased ventilation
main cause of death
scoliosis as a complication of DMD
in turn respiratory load increases as chest wall compliance decreases
weakened muscles unable to hold spine upright
thoracolumbar junction
develop pelvic obliquity
heart problems as a complication of DMD
decreased efficiency of cardiac muscle
ventricular dysfunction
heart block
malignant arrhythmias
swallowing problems/dysphagia as a complication of DMD
weak pharyngeal muscles
nutritional problems
aspiration pneumonia
difficulty walking as a complication of DMD
may lead to wheelchair use
investigations of DMD diagnosis
creatine kinase
muscle needle biopsy
electrocardiogram
echocardiogram
electromyography
genetic testing
MRI
CT
chest X ray
spirometry
creatine kinase testing
take blood sample from vein in arm using needle
small blood volume collected in test tube/vial
significance: creatine kinase is produced during abnormal muscle disintegration such as dystrophy or inflammation
muscle needle biopsy results
in H&E: centrally nucleated myofibers, inflammatory cell infiltration, variable myofiber size, endomysium and perimysium, connective tissue deposits
in MT: increase fibrosis, blue
fluorescence testing: lack of dystrophin
fluorescence testing: variation in myofiber size
A-D shows healthy muscle
E-H shows DMD
electrocardiogram
attaches electrodes to arms, legs and chest to measure the electrical activity of the heart
checks irregular heartbeat and reveals any damage
DMD patients: persistent or labile sinus tachycardia= most common arrhythmia
atrial fibrillation or flutter may also occur
echocardiogram
scan of heart using sound eaves
clear picture of heart muscles and valves
heart structure and function are checked
allows to identify LV dilation
electromyography
measures electrical impulses along nerves to test how nerves and muscles work together
genetic testing
looks for abnormality in DNA of gene responsible for dystrophin production
protein mutated so isn’t produced
standard blood draw
can diagnose genetic condition
can help learn if you have a chance of child inheriting disorder
MRI scan
can help identify affected muscles and the extend of muscle damage
CT scan
series of X rays to create detailed image to view muscle damage
chest X ray
useful to look for breathing or heart symptoms
spirometry
measures amount of air you can breathe out from lungs and how fast you can blow it out
different pharmacological management strategies
corticosteroids
aminoglycosides
myotonia relieving drugs
corticosteroid examples in this case
deflazacort
prednisolone
aminoglycosides
gentamicin
manage respiratory problems
prevent bacteria from producing proteins necessary for growth
reduce risk of infection in respiratory tract
myotonia relieving drugs
mexiletine, phenytoin, baclofen, quinine, dantrolene
short term relief of muscle spasms and weakness
block signals sent from spinal cord to contract muscles
dantrolene: interferes with muscle contraction
corrective surgeries
tendon or muscle release when contractures are severe enough to lock a joint or impair moving
individuals with emery-dreifuss/ myotonic dystrophy may require a pacemaker
surgery to reduce pain and postural imbalance caused by scoliosis
people with myotonic dystrophy often develop Cataracts so may need surgery
cataracts
clouding of lens
meaning light is blocked
exon skipping
skip over mutated exons, sections of the dystrophin gene
to produce functional dystrophin protein
uses anti-sense olginucleotide AON which binds to specific exon to be skipped and helps to change the way RNA is processed
genetic counselling
education about inheritance, change of recurrence and family planning options
coordination of genetic testing for affected individuals and possible carriers
interpretation of genetic test results
counselling to explore emotional/family issues
research opportunities (clinical trials) counsellors can help families determine which studies or trials are available
occupational therapy
may recommend: wheelchair, braces, adaptive equipment to improve mobility and independence
also teach patient how to use equipment, may promote independence/ manage complications
start therapy early and continue through the patient lifetime
physiotherapy
help slow progression of muscle degeneration, improve mobility and reduce risk of contractures and scoliosis
start as early as possible and continue through patients life
speech and language therapy (SALT)
initial assessment of swelling snd communication difficulties
help trying to build on parts of the brain affected
different mobility aids available for DMD patients
canes crutches and walkers
body support and orthotic devices
scooters and wheelchairs
sip and puff devices
canes crutches and walkers
used as walking aids whilst patient is still able to walk
body support and orthotic devices
braces, splints, orthoses enable people to use their less affected/ stronger muscles to perform tasks when other muscles/ joints have became weak
ankle brace/ ankle-foot orthosis is a plastic splint that maintains stability of joint as muscles are too weak, can prolong the time of independent walking
scooters and wheelchairs
standing wheelchairs allow person to stay at eye level and stretch hips, knees and ankles to prevent contractures
seat elevator wheelchairs allow eye level and more manoeuvrability to lower height to sit at table but are more expensive
can accept free prescribed wheelchairs, contribute cost to more expensive wheelchair of choice and they are in charge of chairs and maintenance
contribute cost of more expensive wheelchair but NHS pay maintenance and is from a select range
electric scooters vary form manual and power for good upper body strength or joystick for others
sip and puff devices
hard short sip/ puff into straw like device will move chair forwards and back
soft long sip/puff moves chair left or right
other devices and adaptations offered
voice assistances
enlarged grips for eating and writing utensils
ramps
hoists and lifts
walk in showers
shower seats/ wheelchairs
hand/wrist braces
zippers instead of buttons on clothes
prevalence of DMD
males most exclusively
1in 3500 male births
onset aged 3-5
median death aged 24> in US but the life expectancy is increasing
genetic musculoskeletal disorders
achondroplasia
DMD
osteogenesis imperfecta
Becker muscular dystrophy BMD
emery-dreifuss dystrophy
fasciocapulonumeral muscular disorder FSHMD
Becker muscular dystrophy BMD
insufficient protein dystrophin in muscle
not completely absent but not enough for complete normal muscle function
in frame mutation Xp21.2 locus, dystrophin gene
X linked recessive
later onset and milder symptoms
males have the disease and females are carriers
diagnosis perhaps in later childhood as children become symptomatic later
death in 30s to 40s
