Other Myopathies Flashcards
Myasthenia gravis typically affects females at age ___
It typically affects males at age ___
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 destruction of acetylcholine receptors at the neuromuscular junction?
Decreased surface area, increased gap between nerve ending and muscle
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
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)
How does thymoma affect 15% of patients with myasthenia gravis?
Residual thymus is a benign tumor but increases T cells
What is the mortality of myasthenia gravis?
What will likely cause mortality in someone with myasthenia gravis?
Mortality is about 10%, usually due to respiratory insufficiency
Myasthenia gravis may be comorbid with ___
other autoimmune conditions
Approximately 15% of patients with myasthenia gravis have a ___
thymoma (benign tumor, residual thymus)
What are some treatments for myasthenia gravis?
- Thymectomy
- Corticosteroids
- Methotrexate
- Anticholinesterase drugs
What is myositis ossificans?
Metaplasia of soft tissue to bone following trauma/contusion (usually crushing injury)
Myositis ossificans can occur in tendons, ligaments, fat, fascia, joint capsule etc.
Where does it most often occur?
Muscle
What are the three primary stages of myositis ossificans?
- Pseudosarcoma
- Differentiation
- Maturation
myositis ossificans
Pseudosarcoma begins with ___
trauma, often blunt trauma (crushed or torn) (forming hematoma)
myositis ossificans
After trauma, there is extensive damage and cell death during pseudosarcoma
How is the sarcolemma affected?
Holes appear in sarcolemma sheath and fluid accumulates
myositis ossificans
During pseudosarcoma, holes appear in sarcolemma sheath and fluid accumulates
What makes these holes larger?
Phagocytes invade
myositis ossificans
Where in the pseudosarcoma is the greatest damage?
The center of injury
myositis ossificans
During pseudosarcoma, damaged tissue is liquefied and replaced by ___
sheets of non-specific cells
myositis ossificans
The process of pseudosarcoma can be aggravated by:
- trauma
- massage
- stretching
- surgery
- excess activity
- ultrasound
myositis ossificans
After 15 days of pseudosarcoma, there is extensive proliferation of ___
mesenchymal tissue
(and minimal osteoid formation)
myositis ossificans
Pseudosarcoma often looks like neoplasia histologically
Radiographically it can look like ___
periosteal reaction (hazy ossification in soft tissue)
myositis ossificans
Pseudosarcoma can easily be confused with an ___
osteosarcoma
look for history of trauma
myositis ossificans
When does differentiation occur?
2-3 months post surgery
myositis ossificans
During differentiation, mesenchymal cells become ___
fibroblasts, chondroblasts, and osteoblasts (metaplasia)
myositis ossificans
Which cells remove debris during differentiation?
Giant cells
myositis ossificans
How does the periphery of the injury behave during differentiation?
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
- Opposite of neoplastic process (osteosarcoma ossifies from the inside out)
myositis ossificans
During maturation, a ___ is developed that separates the injury from surrounding tissues
periosteum (mature trabecular and cortical bone)
myositis ossificans
Once a periosteum has developed during maturation, separating the injury from surrounding tissues, what are some ways it may progress?
- May remain indefinitely
- May shrink and disappear (not problematic)
- 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
Fibrodysplasia ossificans progressiva is also known as ___
progressive myositis ossificans
How common is progressive myositis ossificans?
Rare
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 ___
ossified (sheet-like)
When do progressive myositis ossificans symptoms begin in life?
Childhood (as early as age 2)
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
denervation
Nerve root avulsion and compressive neuropathies both affect which neurons?
Lower motor neurons
Amyotrophic 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 is the condition?
Denervation
denervation
If reinnervation does not occur, what happens?
Atrophy progresses and muscle fibers are replaced by adipose tissue
How do denervated fibers initially present?
How do they present as the disease progresses?
Initially scattered irregularly, but cluster as disease progresses
denervation
What is fiber-type grouping?
As one motor neuron takes over a given field of fibers, fiber types group together
