Inflammatory Myopathies Flashcards
Dermatomyositis, polymyositis, and inclusion body myositis are all examples of ___.
inflammatory myopathies
How common are inflammatory myopathies?
Uncommon, 1 in 100,000 annually
Are inflammatory myopathies suppurative?
Nonsuppurative inflammation
Inflammatory myopathies have what four characteristics?
- Presence of inflammatory cells
- Necrosis and phagocytosis of muscle fibers
- A mixture of regenerating and atrophic fibers
- Fibrosis
Which muscles commonly experience weakness with inflammatory myopathies?
Symmetrical proximal muscles (shoulders, hips, torso) (can eventually go distal)
How do inflammatory myopathy symptoms progress over time?
- Gradually increasing symptoms over weeks or months
- Progressive difficulties with activities of daily living (lifting object, climbing stairs, combing hair, holding head up)
Inflammatory myopathy lab results show increased levels of:
- serum muscle-derived enzymes
- ESR
- (maybe) C-reactive protein
Inflammatory myopathies are commonly comorbid with ___.
other autoimmune conditions (antibodies tested to determine which)
How are inflammatory myopathies generally treated?
- Corticosteroids
- Immunosuppressant drugs (DMARDs)
- IV immunoglobulin
Which inflammatory myopathy has no effective therapy?
Inclusion body myositis
Does dermatomyositis more often affect children or adults?
Adults
Which sex is more often affected by dermatomyositis?
Females
Dermatomyositis is likely comorbid with ___.
systemic sclerosis or other autoimmune disorders
A 22-year-old female presents with a rash on her upper eyelids, face, trunk, and some other areas where the sun hits. It is known that she has systemic sclerosis, but now there is evidence of necrosis of skeletal muscle tissue and fiber atrophy.
What is the likely diagnosis?
Dermatomyositis
A 30-year-old female complains of progressive difficulty performing physical tasks over the past four months. She has a bit of a rash on her face which she says is also on her shoulders. She also reports difficulty swallowing solids recently. Lab tests reveal an elevated ESR and presence of serum muscle-derived enzymes.
What is the likely diagnosis?
Dermatomyositis
What is the etiology of dermatomyositis?
Autoimmune
there is no one explanation
With dermatomyositis, compliment mediated (humoral immunity) antibodies attack ___ of skeletal muscle.
microvasculature
angiopathy, microangiopathy
this is not vasculitis/inflammation, it’s break down
With dermatomyositis, ___ attack microvasculature of skeletal muscle (angiopathy).
compliment mediated antibodies (humoral immunity)
Dermatomyositis involves ischemia of ___ which leads to ___ and ___.
ischemia of individual muscle fibers which leads to necrosis of skeletal muscle tissue and fiber atrophy
When dermatomyositis is causing ischemia of individual muscle fibers, necrosis of that skeletal muscle tissue, and fiber atrophy will occur.
Which muscles are often first to be affected?
Gluteal muscles
Why might infarcts occur with dermatomyositits?
Due to involvement of large intramuscular arteries
How might dermatomyositis affect structures other than muscle?
Similar process will affect other other tissues and organs
e.g. difficulty swallowing solids due to diaphragm damage
diaphragm would cause mechanical/muscular dysphagia
What is the etiology of polymyositis?
Autoimmune
Polymyositis almost always begins after age ___.
20
Which sex is predominantly affected by polymyositis?
Females
Does polymyositis involve a skin rash?
No
Does polymyositis involve angiopathy?
No
With polymyositis, ___ directly attack muscle fibers.
T cells
What is represented histologically in polymyositis?
- Necrosis
- Phagocytosis (macrophages present)
- Regeneration
- Fibrosis
Does polymyositis progress systemically or locally?
Systemic progression
Polymyositis has similar muscle inflammation as that seen in ___ infection.
HIV
What is the nature of degeneration associated with polymyositis?
Degeneration is scattered, and not always in the areas of inflammation
Will polymyositis first present more proximally or distally?
Proximally
A 28-year-old female presents with her primary complaint being progressive muscle weakness and diffuse pain in both shoulders. Upon examination, there is evidence of weakness in both of her hips as well. Suspecting this may be systemic, she is sent for lab testing which reveals an elevated ESR and presence of serum muscle-derived enzymes.
What is the likely diagnosis?
Polymyositis
no rash mentioned
Polymyositis is the same as dermatomyositis without the presentation of ___.
rash
What is the most common inflammatory myopathy in geriatrics?
Inclusion body myositis
Inclusion body myositis most commonly presents at what age?
Over age 50
Which sex is predominantly affected by inclusion body myositis?
Males
Inclusion body myositis involves the presence of specific antigen on ___.
sarcolemma
How are T cells related to inclusion body myositis?
What is this similar to?
T cells attack skeletal muscle fiber; similarly to polymyositis
Inclusion body myositis histologically shows ___ in the ___ of involved muscle fibers and near ___.
basophilic granular inclusions in the cytoplasm or nuclei of involved muscle fibers and near vacuoles
Inclusion body myositis primarily involves which regions of the body?
Distal muscles: hands and feet
A 55-year-old male presents with atrophy of skeletal muscle tissue in his hands. Upon biopsy, the involved muscle fibers show basophilic granular inclusions containing intracellular B-amyloid plaque throughout the cytoplasm and nuclei.
What is the diagnosis?
Inclusion body myositis
What is found in the basophilic inclusions of muscles affected by inclusion body myositis?
- B-amyloid plaque
- Tau proteins and other proteins associated with Alzheimer present
- Parkin (associated with Parkinson disease) and the prion precursor protein have also been found
What are the ESR and CRP levels in someone with inclusion body myositis?
Elevated
How does inclusion body myositis respond to therapy?
Poorly
