Pathology II Myopathy Flashcards
Denervation atrophy
Any process that affects anterior horn cells or axon in PNS
Spinal injury - Alpha motor neuron is not innervating the muscle due to spinal injury , therefore muscles will atrophy
LMN muscle atrophy
A 1 year old baby cannot sit up and show muscle weakness. Considered to have flaccid paralysis in the trunk and limbs and lack of sucking ability . Has respiratory failure
Werdnig-Hoffman autosomal recessive disease
Congenital disease -early onset at birth to 4months
Death within 3 years
floppy baby syndrome is presented
Muscles of the mouth don’t work
What diagnostic findings associated with Hoffmann disease?
Muscle biopsy
Will show atrophy of muscle cell
Type I spinal motor atrophy
Degeneration of the cells in the anterior horn of the spinal cord and the motor nuclei in the brainstem
Afferent neurons don’t synapse to anything
Group of inherited disorders
- beginning in childhood
- progressive weakness and wasting of muscles
What kind of stretch reflex result will be present in spinal motor atrophy?
No reflex
Tx for Hoffman
Not available
From what condition do floppy infants generally die?
Respiratory failure
On a biopsy, what is the name of thedistinctive atrophy seen for werdnig-Hoffman disease?
Grouped atrophy muscle
Grouped atrophy
Nuclei of the muscle fibers are in the periphery
Not all muscles atrophy
Atrophy occurs from disuse of the muscles
What are the two categories of muscular dystrophies?
Type I spinal cord atrophy
X-linked
What type of motor lesion don’t cause muscle atrophy?
UMN
A 16 year presents with muscle biopsy that shows no dystrophin, muscle fiber size variations, nuclei centrally located, increased connective tissue
Duchenne’s
Which is a more severe and common disease
A 16 year old has trouble contracting muscles. The disease was presented in his grandfather.
2/3 familial cases
X-linked
What happens to the muscle fibers in Duchenne’s?
Regeneration of muscle fibers
Turnover of fibers occur because they become necrotic and phagocytosis
Turnover rate exceed regeneration =overall decrease in muscle fibers
Normal skeletal muscle biopsy
Cross section view reveals multiple nuclei of the fiber are at the periphery of the muscle fiber
What is found on a muscle biopsy of Duchenne’s and beckers
Variation of muscle fiber size Increased endomysial connective tissue -bluish area Heterogenous tissue Nuclei centralize Regeneration of fibers
What does western blotting reveal for Duchenne’s vs Becker’s
Dystrophin is absent in Duchenne’s and low amount in Becker’s
What uses antibody to the muscle dystrophin to view gold stain?
Immunoperoxidase stain
Useful in Duchenne’s diagnostic
Where is The gold stain seen in immunoperoxidase stain located ?
Periphery of the normal muscle fibers
If missing, suspect Duchenne’s
The gold stain is present in small amounts in the patient
Suspect Becker
Some muscle cells will have low amnt of dystrophin
Altered dystrophin
Becker’s
A teen complaints of muscle weakness in pelvic and it also extends to the shoulder
A Major early complaint of people with Duchenne’s
At later stages of DMD, BMD, what happens to the muscle fibers?
Muscles get replaced by fat and connective tissue
What is the protein found in serum that tells you whether or not the muscles are going necrosis?
Creatine kinase
In Duchenne’s, what is present at high levels and peaks early and then absent at later stages as muscle mass decreases?
Increased Creatine kinase in the first decade
Decreased CK Because muscles die
A teen presents with large calf and his muscle biopsy shows that fibers are increased and fat and connective tissue present
Pseudohypertrophy
Not muscles per se that hypertrophy
It is the tissue
In Duchenne’s, chronic inflammation is present. What will be seen in the biopsy ?
Degeneration of muscle fibers along with some regeneration - scattered
Hypertrophy of muscle fibers- larger contracted fibers
Fibrosis
Lymphocytes
Macrophages?
Early development shows proximal muscle weakness
Duchenne’s in early childhood
what other conditions cause death in pts with muscular dystrophy
Infection
Cardiac failure
A 60 year old have weakness, a slowly progressive disease. His brother may have had Sx
Becker’s
Wheelchair by age 10
Duchenne’s
Most common form of dystrophy In Adults
Myotonic dystrophy
A patient shakes hand but can’t let go because of impaired muscle relaxation
Myotonic dystrophy
What happens to the muscle fibers in DM
Atrophy of type I fibers
Hypertrophy of type II fibers
Duchenne’s vs DM on biopsy
Muscle fibers are not necrotic or regenerated as much in DM
A patient presents with stiffness and unable to relax grip from handshake, facial and jaw muscles are affected most, and he has cataracts
Multi system affect
The patient has DM
A 40 year old presents with frontal balding, hatchet facies due to atrophy of temporis muscle, ptosis, drooping mouth due to facial weakness, cataracts, wasting of sternlcleidomastoid, and gynecomastia
Clinical signs of myotonic dystrophy
How to determine gyencomastia in pts with DM?
Palpation of breast tissue
What is a physical exam for DM ?
Percussion of thener muscles
A 60 year old pt’s thumb moves sharply into opposition and adduction and slowly returns to initial position on percussion of thener muscles
Pt has myotonic dystrophy
A 6 month old baby has a tented, inverted V shape of upper lip, and pyramidal lip shape
Acquired disease in rare form
Infant has Myotonic dystrophy
Pt’s lab results show presence of central nuclei in the muscle fibers in cross section (The centralized nuclei are arranged in longitudinal fashion) along with variation in fiber size, fibrosis
Myotonic dystrophy
What is a major differential for Myotonic vs muscular dystrophies ?
Size of the fibers are homogenous
What are toxic myopathies?
Thyrotoxic myopathy
Ethanol myopathy
Drug-induced myopathy
A patient presents with proximal muscle weakness, exophthalmos, muscle cramps, and slow movement and reflexes
Thyrotoxic myopathy - a thyroid dysfunction
Males are 4x affected
Which clinical Sx presents before exophthalmos in thyrotoxic myopathy ?
Proximal muscle weakness
Grave’s disease
Increased production of thyroid hormones T3 and T4 Metabolic rate goes up Heat Intolerant Fat and muscle breakdown Weight loss
Is thyrotoxic myopathy similar to grave’s disease?
Yes or no?
An intoxicated pt presents was taken into ER. His urine results show that it is red
Ethanol myopathy, specifically acute myopathy
Myoglobinemia is suspected because of urine result
The increasing level of myoglobin indicates
What results from binge drinking ?
Acute myopathy
Renal failure
What is rhabdomyolysis?
Cause muscle breakdown
Associated with acute myopathy from binge drinking
What class of drugs induce myopathy?
Steroids
Chloroquine (anti malarial)
How do steroids affect muscles?
Cause them to breakdown
Results in muscle weakness
Type 2 muscle fibers atrophy
What is the best defined autoimmune disease?
Myasthenia gravis
Ab are made against Ach rcpts which are eventually degraded by cells
Efferent discharge (parasympathetic) usually release Ach
What occurs in the thymus gland in people with MG?
- Thymic gland undergoes hyperplasia (65%)
Produce Ab
Remove the thymus to tx MG-will cure MG only if the source of Ab production is from the thymus - Thymic tumor
What is the first sign of MG?
Extraocular muscles -Ptosis -Diplopia- double vision Generalized weakness Respiratory compromised Low nerve conduction with repetitive stimulation
A pt. presents with ptosis, Diplopia, and weakness overall
MG if tx with anti-Acholinesterase improve condition
A major cause of death in pts with MG
Respiratory compromise
What is the expected survival for MG pts?
95% 5 year survival
What EMG finding will indicate MG?
Repetitively stimulate a nerve in MG and the velocity of the conduction will decrease
What is the rationale for tx MG with anti-Achase?
Increase amnt of Ach - allowing Ach linger and bind to rcpts
What are the other two drugs used to tx MG
Prednisone- glucocorticoid
Plasmapheresis - remove Ab from the circulation
Lambert Eden syndrome
Disease of neuromuscular junction
Develops as paraneoplastic process
Proximal muscle weakness
Autoimmunity to ca2+ may be responsible
What is the paraneoplastic process?
Lung cancer
Small cell carcinoma of lung (60%)
How does EMG finding in Lambert Eden distinguish from MG?
The velocity of conduction is increased with repetitive stimulation
A pt presents with proximal muscle weakness and known to have autonomic dysfunction. No sign of improvement shown with anticholinerase. What is mechanism of the disease?
Can’t release Ach because Ca2+ channels blocked?
In what disease will Chemo and radiation best extend the life to one year in pts
Lambert Eden
What’s the rationale for increased EMG in lambert Eden ?
Initially no change in nerve conduction
Stimulation of 10s or more will lead to calcium being let into cell allowing the release of Ach, perhaps something to do with the build up of Ach in the terminus, which eventually going to be released when the electrical stimuli overrides it
