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69 Cards in this Set

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What is the difference between primary and secondary myopathies?
Primary -- defect in muscle structure/function

Secondary -- acquired muscle dysfunction
(due to something outside of the muscle itself, ie toxins)

NOTE: same distinction applies between primary and secondary neuropathies
What clues can be used to differentiate myopathies from neuropathies (3)?
Myopathy -- motor, proximal, no autonomic involvement

Neuropathy -- motor & sensory, distal, often autonomic involvement
What is pseudohypertrophy?

What is it a sign of?
When muscle seems to be enlarged
Actually due to replacement of muscle by fat/connective tissue

Sign of myopathy
What is myotonia?
Delayed relaxation of muscles
What are muscular dystrophies defined as?
Primary, genetically transmitted diseases
Entail a progressive muscle wasting and weakness
Duchenne's and Becker dystrophies are due to mutations in what?
Dystrophin gene
Different characteristics of Duchenne vs. Becker dystrophies
--- Duchenne --
SEVERE, manifests by ~ 5 y.o., rapidly progressive
wheelchair dependence by 10-12 y.o., death in early 20s

--- Becker ---
MILD, onset in late childhood, slower progression
Many pts. have nearly normal lifespan
How do people w/ Duchenne dystrophy present at birth?
How are Duchenne and Becker dystrophies transmitted?
X-linked inheritance

NOTE: female carriers CAN have myopathic symptoms
What other body parts can Duchenne and Becker dystrophies affect (2)?
(beyond skeletal muscle)
Cardiac muscle and brain
SO, pts. can also have cardiomyopathy and mild mental retardation

NOTE: cardiac disease is much rarer in Becker MD
Limb girdle dystrophies are due to defects in what?
(part of the dystrophin complex)
Congenital muscular dystrophy is due to defects in what?
(part of the dystrophin complex)
Merosin (laminin-2)
What does the dystrophin complex do?
Links the actin cytoskeleton to the extracellular matrix
What is the most common adult-onset muscular dystrophy?
Myotonic dystrophy
What genetic abnormality is present in myotonic dystrophy?
Trinucleotide repeat (CTG) expansion

n > 50 repeats equal disease
What is Pompe disease?
A congenital myopathy

Deficiency in acid maltase
What are the big three INFLAMMATORY myopathies?
Inclusion body myositis
What is the pathophysiology of dermatomyositis?
Immune complexes deposit in capillaries of muscle and skin
(entails perivascular B and T cells)

Damaged capillaries cause muscle ischemic damage
(happens particularly at the periphery)

NOTE: dermatomyositis affects BOTH kids and adults
What is the pathophysiology of polymyositis?

How does it present histologically?
Cytotoxic T cell attack on muscle cells

Endomysial infiltrates, plus scattered atrophy
What is the treatment for polymyositis?
Responds to steroid treatment
What group of people does polymyositis affect most?
Adults, F > M
What group of people does inclusion body myositis affect most?
Adults, M >> F (3x)
How does inclusion body myositis differ from polymyositis?
Affects males more
Has more distal involvement
Has a highly specific pattern of rimmed vacuoles and/or inclusions
Is NOT responsive to steroid treatment
Inclusions in inclusion body myositis resemble those found in what disease?
What is the pathophysiology of Mcardle's disease?
Deficiency in the phosphorylase that breaks down glycogen
What is the main therapy for Mcardle's disease?
Dietary management
What type of exercise can people w/ Mcardle's not tolerate?

What does doing this type of exercise cause?
Can't tolerate brief and intense exercise

Causes cramping, and muscle swelling
How is Mcardle's disease inherited?
RECESSIVE inheritance
What group of people does Mcardle disease affect most?

Onset is @ < 15 y.o.
How is Pompe's disease inherited?
RECESSIVE inheritance
What are the three types of Pompe's disease?

Which is the most serious?
Infantile onset
Childhood onset
Adult onset

Infantile onset is the most serious
(usually, pts. die before 1 year of age)
In infantile Pompe's, where does glycogen accumulation occur?
In most tissues

There is pronounced heart and liver involvement
How can infantile Pompe's present?
Cardiomegaly & CHF
Liver involvement
Weakness & hypotonia
In childhood onset Pompe's, where does glycogen accumulation occur?
Mainly in muscle
How does childhood onset Pompe's present?
Proximal, symmetric weakness (large muscles)
In what age range do pts. w/ chilhood Pompe's die?

What do they die of?
From age 3 - 24

Die of respiratory failure
How does adult onset Pompe's present differently in young and old adults?
Young adults -- fatigue

Old adults -- proximal weakness
What group of muscles does adult onset Pompe's affect?
Paraspinous muscles (causes atrophy)
What is carnitine, and what does it do?
Pseudo amino-acid

It shuttles fatty acids across the mitochondrial membrane
(plays an important role in FA metabolism)
What set of muscles do mitochondrial myopathies often affect?
Proximal muscles

Sometimes, w/ SEVERE involvement of extraocular muscles
What is Kearns-Sayre syndrome?
Ophthalmoplegia plus pigmentary degeneration of the retina

It is a mitochondrial myopathy
What type of inheritance do mitochondrial myopathies show?
Often, MATERNAL inheritance
What is the pathophysiology of myasthenia gravis?
Due to autoantibodies against ACh receptors
What is the pathophysiology Eaton-Lambert Syndrome?
Due to autoantibodies against presynaptic Ca channels

NOTE: this syndrome is usually paraneoplastic
(seems that Abs are triggered by a cancer Ag)
What are differences between chronic vs. acute denervation changes?
Acute cause scattered atrophy

Chronic first cause grouped atrophy
Ultimately, cause fiber-type grouping
What is a dysesthesia?
Condition in which a sense, particularly touch, is distorted

i.e. "pins and needles"
What is Wallerian degeneration?
Degeneration of an axon DISTAL to the site of injury
What is a regenerating cluster?

What is it a sign of?
Several adjacent sprouting axons myelinated by a single Schwann cell

Evidence of axonal damage
What is onion bulb formation a response to?
Schwann cell response to any chronic demyelinating process
What group(s) of people does Guillan-Barre most affect?
Young adults and > 55 y.o.

Male:Female is 1.25:1
How is Guillan-Barre treated?
Plasma exchange or IV IgG
What type of infiltrate would be seen on a Guillan-Barre biopsy?
Macrophagic infiltrate
25% of cases of GBS are preceded by what?
Campylobacter jejuni infection
What pathological findings are seen in CIDP?
(chronic inflammatory demyelinating polyneuropathy)
Early -- lymphocytic & macrophagic infiltrates

Late -- Onion bulbs
How is CIDP treated?
(chronic inflammatory demyelinating polyneuropathy)
Responds to steroids
How does diabetic neuropathy often present?
As a distal, sensory, polyneuropathy
What happens to capillaries in diabetic polyneuropathy?
Capillary walls get thickened and hyalinized
What fibers are most affected in vasculitis neuropathy?
Large, myelinated fibers are most severely affected
How does Charcot-Marie-Tooth disease present?
Loss of muscle tissue
Loss of touch sensation (predominantly extremities)
What does connexin32 do?

What do mutations in it cause?
Forms gap junctions

Point mutations in it cause X-linked CMT
(inheritance is X-linked dominant)
What protein is assoc. w/ both HNPP and CMT1A?
(hereditary neuropathy w/ pressure palsies)
(charcot-marie-tooth 1a)

Too little of it causes what?
Too much of it causes what?

Too little (1 copy (due to deletion)) of it causes HNPP
Too much (3 copies (due to duplication)) of it causes CMT-1a
What is revealed on biopsy in HNPP?
(hereditary neuropathy w/ pressure palsies)
Tomaculae -- focal thickening of the myelin sheath
When is the usual onset of HNPP?
(hereditary neuropathy w/ pressure palsies)
Young adulthood
What does protein P0 do?
Helps maintain the structural integrity of the myelin sheath
What are the 3 important peripheral Schwann cell myelin proteins?
When is the usual onset for CMT1A?
(charcot-marie-tooth 1a)
1st decade of life
What is the most prominent initial sign of CMT1A?
(charcot-marie-tooth 1a)
Foot drop

NOTE: leg areflexia is present in 100% of the cases
What does biopsy early vs. late in CMT1A show?
Early -- excess myelin

Late -- myelin loss and onion bulb formation
How is the gene for PMP22 inherited?
Autosomal dominant inheritance