Other Myopathies Flashcards
Myasthenia gravis typically affects females at ages ___.
It typically affects males at ages ___.
Females: 20-30
Males: >50
What is the etiology of myasthenia gravis?
Acquired autoimmune disease
With myasthenia gravis, patients develop antibodies to ___.
acetylcholine receptors
at the neuromuscular junction
myasthenia gravis
What is the result of blocking and subsequent destruction of acetylcholine receptors at the neuromuscular junction?
Decreased surface area and increased gap between nerve ending and muscle
muscle is not inflamed/attacked
A 25-year-old female patient presents with acute abnormal muscular fatigability and weakness. You notice that she has ptosis as well.
Which myopathy is likely?
Myasthenia gravis
A 58-year-old male patient presents with abnormal muscular fatigability and weakness. You notice that he has diplopia and a mask-like expression with a snarl. In his medical history, it is revealed that he has a thymoma.
What is the likely myopathy?
Myasthenia gravis
How are extraocular muscles frequently affected by myasthenia gravis?
- Ptosis
- Diplopia
still have pupillary reflex
If a patient has a mask-like facial expression or snarl and you suspect myasthenia gravis, what should you rule out?
Stroke (with MRI/CT)
Myasthenia gravis may be comorbid with other autoimmune conditions.
If myasthenia gravis is diagnosed, patient should get a chest CT looking for ___.
Hyperthymus/thymoma
15% of patients have a thymoma
removing thymic tissue can solve myasthenia gravis
What are some treatments for myasthenia gravis?
- Thymectomy
- Corticosteroids
- Methotrexate
- Anticholinesterase drugs
improves quality of life
When treating myasthenia gravis, plasmapheresis reduces ___.
anti-Ach receptor antibodies
What is the likelihood of mortality for myasthenia gravis?
What will likely cause mortality in someone with myasthenia gravis?
Mortality is about 10%, usually due to respiratory insufficiency
diaphragm complications
Approximately 15% of patients with myasthenia gravis have a ___.
thymoma
benign tumor, residual thymus
What is myositis ossificans?
Metaplasia of soft tissue to bone following trauma/contusion (usually crushing injury)
not inflammatory or autoimmune
Myositis ossificans can occur in tendons, ligaments, fat, fascia, joint capsule etc.
Where does it most often occur?
Muscle
What are four basic steps describing how myositis ossificans forms bone within muscle after trauma?
- Fibroblasts infiltrate
- Fibroblasts become osteocytes
- Osteocytes make osteoid
- Osteoid mineralizes into bone within muscle
What are the three primary pathogenesis stages of myositis ossificans?
- Pseudosarcoma
- Differentiation
- Maturation
In the first 1-2 months, myositis ossificans can look like ___, so an MRI with contrast is more helpful than x-ray.
osteosarcoma
myositis ossificans
Pseudosarcoma begins with ___.
trauma
often blunt trauma: crushed or torn
common in football
myositis ossificans
After trauma, there is extensive damage and cell death during pseudosarcoma.
Fibroblasts will become osteocytes through metaplasia as a result of ___.
liquefaction
necrosis
myositis ossificans: pseudosarcoma
Given that there was trauma, extensive damage, and cell death within the muscle, ___ will appear in the sarcolemma sheath and ___ accumulates as a result.
holes will appear in sarcolemma sheath and fluid accumulates
myositis ossificans: pseudosarcoma
Due to cell damage and death, holes appear in sarcolemma sheath and fluid accumulates.
What will happen to make these holes larger?
Phagocytes invade
Where in the muscle will there be the greatest damage if a patient is in the pseudosarcoma stage of myositis ossificans?
The center of injury
myositis ossificans
During pseudosarcoma, damaged tissue is liquefied and replaced with ___.
sheets of non-specific cells
The progression of damage due to myositis ossificans in its pseudosarcoma stage can be aggravated by:
- trauma
- massage
- stretching
- surgery
- excess activity
- ultrasound
myositis ossificans: pseudosarcoma
15 days post trauma, there is extensive proliferation of ___ tissue.
mesenchymal
minimal osteoid formation at this time
Pseudosarcoma can easily be confused with ___ radiographically, but can be differentiated with ___.
confused with osteosarcoma radiographically, but can be differentiated with history of trauma
When does the differentiation stage of myositis ossificans occur?
2-3 months post injury
8-12 weeks
myositis ossificans
During differentiation, mesenchymal cells become ___.
fibroblasts, chondroblasts, and osteoblasts
Which cells remove debris during the differentiation stage of myositis ossificans?
Giant cells
myositis ossificans
How does the periphery of the injury behave during the differentiation stage?
How does the center of the injury behave?
Periphery: begins to mineralize
Center: may remain as a fluid filled cyst or filled with undifferentiated cells
myositis ossificans
What is the zonal phenomenon that occurs during differentiation?
Mature bone develops around periphery due to hematoma
This helps rule out osteosarcoma because a neoplastic process develops from the inside out
shows nicely on CT
During the maturation stage of myositis ossificans, a ___ is developed that separates the injury from surrounding tissues.
periosteum (mature trabecular and cortical bone)
limits contractility/motion/function
Once a periosteum has developed during maturation of myositis ossificans, separating the injury from surrounding tissues, what are some ways it may progress/resolve?
- May remain indefinitely
- May shrink and disappear (rarely)
- May be surgically removed (once matured, too early and it will return)
What are some clinical manifestations of myositis ossificans?
- Pain in the muscle
- Decreased ROM
- Hard palpable lump may be found deep in the muscle
- Can be associated with neurological disease (especially with wheelchair)
A patient’s radiograph of their femur presents a hazy cloud appearance that is hard to differentiate. It may be an osteosarcoma, but it may be myositis ossificans.
What are some options moving forward?
- Watch and wait
- Get MRI
Fibrodysplasia ossificans progressiva is also known as ___.
progressive myositis ossificans
How common is progressive myositis ossificans?
Rare
incredibly
What is the etiology of progressive myositis ossificans?
Some cases are inherited; no history of trauma
Progressive myositis ossificans usually involves which muscles?
Postural muscles: back and major joints
With progressive myositis ossificans, muscles become progressively ___ due to ___.
ossified (sheet-like) due to fibroblast metaplasia
Progressive myositis ossificans can present with severe functional disability.
When do symptoms begin in life?
Childhood
as early as age 2 or by adolescence
Progressive myositis ossificans is generally fatal due to ___.
loss of pulmonary function
Denervation affects which muscle fibers?
Both type I and II fibers
Denervation includes multiple disease processes that cause progressive muscle ___.
weakness and atrophy
whole nerve compressed
What are some examples of traumatic and/or compressive denervation?
- Nerve root avulsion, e.g. due to surgery
- Compressive neuropathies. e.g. carpal tunnel, tunnel syndromes
Amylotrophic lateral sclerosis (ALS) and spinal muscular atrophies are both examples of ___.
denervation
Skeletal muscle fibers are separated from lower motor neurons and the cells have atrophied. They appear angular and dark histologically.
What condition is present?
Denervation
denervation
What will result if reinnervation does not occur?
Atrophy progresses and muscle fibers are replaced by adipose tissue
How do denervated fibers initially distribute?
How do they present as the disease progresses?
Initially scattered irregularly, but cluster as disease progresses
What is fiber-type grouping as seen in denervation/reinnervation?
As one motor neuron takes over a given field of fibers, fiber types group together
Muscle changes fiber type due to motor nerve changing
Denervation has caused fiber-type grouping to occur, making one motor neuron take over a field of fibers.
What if denervation continues?
Grouped atrophy will occur
