Term
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Definition
diffuse conditions
-subacute, chornic time course
Muscular dysthrophies
Acquired myopathies |
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Term
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Definition
dystrophin deficiency (Duchenne's, Becker's)
limb-girdle & other regional dystrophies
myotonic dystrophy |
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Term
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Definition
metabolic
inflammatory
-dermatomyositis
-inclusion body myositis
-polymyositis |
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Term
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Definition
a disease in which the structure or function of muscle is compromised
damage to the muscle
may be either hereditary or acquired |
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Term
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Definition
an inherited, progressive disorder of muscle, usually due to an abnormaility in a structural protein
all MDs are hereditary myopathies (but NOT all hereditary myopathies are MDs) |
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Term
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Definition
dystrophin deficiency (Duchenne's, Becker's)
limb-girdle & other regional dystrophies
myotonic dystrophy |
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Term
Duchenne's MD
clinical features |
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Definition
boys only, X-linked disease
normal at birth, clinical manifestation start as motor function "develops"
at onset of walking:
-remain clumsy longer than normal
-Gower's sign
-never run normally, can't fully jump off floor
calf pseudohypertrophy
gradual deterioration in respiratory function; cardiac abnormalities; mild non-progressive cognitive impairment |
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Term
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Definition
when standing from the floor:
-get on hands and knees
-stretch legs out behind
-walk hands up legs to get upright |
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Term
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Definition
calf muscles firm and rubbery
look muscular, but not really |
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Term
Duchenne's MD
clinical course |
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Definition
age 2-6: gain motor skills as normal development outpaces the disease
age 6-7: start to fall w/o warning
age 8-10: lose ability to climb stairs or stand from floor
wheelchair bound by age ~12: contractures, scoliosis, skeletal deformities |
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Term
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Definition
most patients dies in late teens - 20's
usually due to respiratory failure
occasionally due to cardiac failure |
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Term
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Definition
prednisone beneficial - though duration of benefit unknown, appreas to last ~3 years
supportive care: PT, bracing, surgical reconstruction
(gene therapy still experimental) |
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Term
Becker's MD
clinical features |
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Definition
similar to Duchenne's, but milder
later symptom onset (~12 years, some not until 40's)
often complain of muscle cramps
independent walking until late teens
cardiomyopathy common
cognition usually normal |
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Term
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Definition
| usually live until 50's, sometimes later |
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Term
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Definition
degeneration and phagocytosis of single muscle fibers or groups of fibers
the necrosis stimulates a regenerative process - basophilia of the cytoplasm, hyperplasia, and nucleolation of nuclei; presence of myotube, myocytes
as disease progresses - loss of muscle fibers, residual fibers variable in size, fibrosis, ingrowth of adipocytes |
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Term
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Definition
| problems with dystrophin, which affects normal muscle action |
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Term
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Definition
actin-myosis form thick and thin filaments in alternating layers with cross-bridges that attach/detach
ratcheting action that cases the filaments to slide over each other, shortening the contractile unit
dystrophin-associated protein complex stabilizes the muscle membrane to the extracellular basal lamina during contraction/relaxation |
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Term
MD pathpphysiology
Duchenne's |
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Definition
deletion in the gene that codes for dystrophin --> absence of dystrophin
self-sustaining cycle:
-focal tears during contractile activity
-massive influx of extracellular Ca
-activation of proteolytic enzymes
-initiation of chain of destructive processes
-muscle fiber necrosis
-increased activity in spared muscle fibers
-back to top! |
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Term
MD pathophysiology
Becker's |
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Definition
| mutation in dystrophin gene, but preserved reading frame --> dystrophin present, but structurally abnormal |
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Term
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Definition
increased creatine kinase (releases in muscle breakdown)
myopathic EMG chagnes (smaller, faster bc not have smaller motor units)
muscle bx with anti-dystrophin staining |
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Term
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Definition
steroids not typically used
goal of management is maximization of mobility
-OT
-bracing
-surgical reconstruction
(used less often than with Duchenne's) |
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Term
| limb-girdle muscular dystrophies |
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Definition
various mutation sin dystrophin-associated protein and other muscle proteins
specific mutations can affect age of onset, pattern of muscle involvement
hereditary disorders that casue progressive dysfunction of trunk and proximal muscles |
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Term
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Definition
| prolonged muscle contraction (delayed relaxation) after a voluntary contraction or percussion of the muscle |
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Term
myotonic dustrophy
clinical features |
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Definition
autosomal dominant
weakness and atrophy
myotonia
multisystem abnormalities |
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Term
myotonic dystrophy
pattern of weakness |
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Definition
ptosis
mm of eyes and mouth closure
temporalis
small mm of hands
extensor mm of forearms
SCM
mm of larynx and pharynx |
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Term
myotonic dystrophy
multisystem abnormalities |
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Definition
cataracts
cardiac conduction defects/arrhythmia
testicular atrophy
early male baldness
impaired glucose tolerance/DB
mild/moderate MR |
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Term
myotonic dystrophy
pathogenesis |
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Definition
elongated trinucleotide repeat (CUG)
abnormal RNA transcript binds to proteins involved in RNA-splicing; interfere with splicing of RNA of other genes
-cholride channel (myotonia)
-insulin receptor (IGT)
-other genes, likely leading to other manifestations |
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Term
myotonic dystrophy
diagnosis |
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Definition
myotonic discharges on EMG
genetic testing |
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Term
myotonic dystrophy
management |
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Definition
primarily supportive
it myotonia is annoying enough to treat, certain meds available |
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Term
| non-dystrophic hereditary myopathies |
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Definition
abnormal glycogen metabolism (cramps with exercise, relatively asymptomatic at rest)
PFK deficiency (unabel to break down gluc/FFA fast enough)
mitochondrial myopathies (problem with energy generation)
channelopathies (periodic paralysis,. myotonic disorders) |
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Term
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Definition
metabolic
inflammatory
-dermatomyositis
-inclusion body myositis
-polymyositis |
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Term
acquired myopathies
metabolic |
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Definition
*Cushing's syndrome
*exogenous steriods
hypothyroidism
hyperthyroidism
hyperparathyroidism
chronic alcohol use |
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Term
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Definition
dermatomyositis
inclusion body myositis
polymyositis |
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Term
dermatomyositis & polymyositis
clinical features |
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Definition
symmetric proximal muscle wasting and weakness
gradual progression (D: weeks, P: months)
pain common, but not severe
D: characteristic rash on face and hands |
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Term
inclusion body myositis (IBM)
clinical features |
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Definition
prominent involvement of forearm flexors and knee extensors
often asymmetric
dysphagia common
mild facial muscle involvement also common |
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Term
inflammatory myopathies
epidemiology |
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Definition
dermatomyositis most common in children-young adults
IBM onset common after age 50
adult onset derm. often with systemic malignancy |
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Term
inflammatory myopathies
pathology |
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Definition
segmental muscle fiber necrosis
muscle fiber regeneration
mononuclear cell inflammation |
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Term
inflammatory myopathies pathology
dermatomyositis mononuclear cell inflammation |
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Definition
humorally mediated
inflammatory cells around blood vessels and between muscle fascicles (arond outside of fibers)
micro infarcts may occur |
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Term
inflammatory myopathies pathology
polymyositis mononuclear cell inflammation |
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Definition
cell-mediated
inflammatory cells among/infiltrating muscle fibers |
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Term
inflammatory myopathies pathology
IBM mononuclear cell inflammation |
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Definition
cell-mediated
inflammatory cells among/infiltrating muscle fibers
*protein aggregates*
-vacuolar inclusions in muscle fibers contain beta-amyloid, tau, TDP-34 |
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Term
infalmmatory myopathies
diagnosis |
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Definition
increased serun creatine kinase
myopathic EMG changes
muscle bx for definitive diagnosis |
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Term
inflammatory myopathies
management |
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Definition
all get symptomatic treatment
prednisone fro derm, poly (with immunosuppressants as second line)
none known for IBM |
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