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Diseases of Skeletal Muscle
Anne Buckley MD PhD
Neuropathology
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Normal muscle architecture
anatomyforme.blogspot.com
emedicine.medscape.com
Type 1 and Type 2 fibers (ultrastructure)
Type 1
Aerobic, oxidative
Abundant, large mitochondria
Numerous lipid droplets
Type 2
Anaerobic, glycolytic
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Type grouping & grouped atrophy
His
tolo
gy for
Path
olo
gis
ts
Courte
sy E
d B
ossen
Atrophied fibers
Histopathology of
neurogenic atrophy
Normal
www.pathology.vcu.edu
How fiber type grouping occurs
in denervating (neurogenic) disorders
Peripheral nerve damage
• Diabetes mellitus
• Demyelinating disorders
Motor neuron disorders
• Amyotrophic lateral sclerosis (upper & lower motor neurons)
• Spinal muscular atrophy (lower motor neurons)
http
://bra
inm
ind.c
om
Causes of
neurogenic atrophy
Spinal Muscular Atrophy (infantile motor neuron disease: SMN1 mutations)
SMA Type 1 (in utero … 3 years)
SMA Type 2 (3 months … 4+ years)
SMA Type 3 (2+ years … adulthood)
Arch Iranian Med (2004) 7: 47
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Muscular dystrophies: >100 disorders of the sarcolemma
http://www.indianews365.com neuromuscular.wustl.edu
Fas
A muscular dystrophy: Duchenne
http://picasaweb.google.com
His
tolo
gy fo
r Path
olo
gis
ts C
ourt
esy E
d B
osse
n
Dystrophin expression
Gower maneuver
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Central core disease (an ion channel myopathy)
Nemaline rod myopathy
Centronuclear myopathy
“Congenital” myopathies
(floppy babies):
http
://ww
w.g
fmer.c
h
ww
w.p
ath
olo
gy.v
cu.e
du
JR
are
Dis
eases (2
00
8) 3
:26
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
A metabolic myopathy:
McArdle Disease (GSD IV)
•Myophosphorylase deficiency
•Exertional myalgia, rhabdomyolysis
Courte
sy E
d B
osse
n
PAS stain for glycogen
H&E stain
A metabolic disorder: Mitochondrial myopathy
www.pathology.vcu.edu
ne
uro
muscula
r.wustl.e
du
http
://cours
e1.w
inona.e
du
Normal mitochondrian
“ragged red” fiber
Paracrystalline arrays
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
An inflammatory myopathy:
Dermatomyositis W
ikim
ed
ia c
om
mons
*Strongly associated with cancer*
Courtesy Ed Bossen
Dermatomyositis
Perifascicular atrophy
Perivascular
inflammation
J N
euro
l N
euro
surg
Psychia
try 2
009
;80:1
186
ww
w.n
eu
rop
ath
olo
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eb.o
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An inflammatory myopathy:
Inclusion Body Myositis
Inclusion body myositis ne
uro
path
olo
gyw
eb.o
rg
ww
w.p
ath
olo
gy.v
cu.e
du
Rimmed vacuoles
Ultrastructure: filaments in vacuoles
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Statin-induced necrotizing myopathy
Colchicine-induced vacuolar myopathy
Steroid myopathy
ne
uro
muscula
r.wustl.e
du
Pra
ct N
euro
l (200
6)6
:4
imag
es.rh
eum
ato
logy.o
rg
Toxic myopathies:
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
A neuromuscular junction disorder:
Myasthenia gravis
ww
w.p
ath
olo
gy.
vcu.e
du
Adams and Victor's Neurology
healthmad.com adkpathcourse.blogspot.com
Normal
motor
endplate
Chapter 27 R&C
1. Neurogenic atrophy
2. Muscular dystrophies
3. “Congenital” myopathies
4. Metabolic myopathies
5. Inflammatory myopathies
6. Toxic myopathies
7. Diseases of the neuromuscular junction
Malignant Hyperthermia
• A hypermetabolic state induced by some general anesthetics
(tachycardia, tachypnea, muscle spasms, hyperpyrexia)
• Patients with inherited muscle disease are predisposed
(dystrophinopathies, metabolic, other congenital myopathies)