Inflammatory Myopathy Flashcards
What is an inflammatory myopathy?
An autoimmune condition where the inflammatory response is directed against either normal muscle fibers alone or many tissues or against the supporting stroma
What is the clinical presentation of polymyositis?
An inflammatory myopathy with symmetric, proximal greater than distal weakness with an onset that can be gradual or rapid
What is the sex ratio of polymyositis?
Femal predominance
What should be in the differential when evaluating for polymyositis?
If there is a lot of pain in joints and muscle: scleroderma, mixed connective tissue disease, lupus, rheumatoid arthritis (rarely)
If there is pulmonary involvement: sarcoidosis
What is the pathology of polymyositis?
Inflammation around normal muscle fibers with other fibers that show necrosis/degeneration/regeneration, and nuclei located centrally (instead of peripherally)
What lab tests should be done to evaluate polymyositis?
Sedimentation rate and anti Jo-1 antibody (as well as tests to evaluate for related systemic conditions)
What is the treatment for polymyositis?
Corticosterioids either oral or IV once a week, can also use azathioprine, methotrexate, or cyclosporine.
What is the clinical presentation of dermatomyositis?
Swallowing difficulty, persistent erythema in sun exposed skin, violaceous/edematous face and eyelids, eczema on extensor surfaces (MCP, elbows, knee, and sacrum)
What symptoms are unique to juvenile dermatomyositis?
Toe walking due to ankle contractures and subcutaneous calcinosis
What is the pathology of dermatomyositis?
Membrane attack complexes in capillaries, perivascular inflammation on a muscle biopsy, perifascicular atrophy
What is the treatment for dermatomyositis?
Similar to polymyositis, cortiosteroids or alternative immunosuppressive agents
What demographic groups are associated with inclusion body myositis?
Male predominance, older age predominance (except for familial variety)
What are the clinical findings of inclusion body myositis?
Distal or asymmetric weakness, predilection for quadriceps more than hip muscles, particular wrist or finger flexor involvement. Disease has slow progression and leads to grip difficulty later in the course.
What is the pathological hallmark of inclusion body myositis?
Rimmed vacuoles on H&E or gomori trichrome stain that are subsarcolemmal and stain with congo red. On EM, there are filaments with a beta amyloid appearance.
What is the treatment for inclusion body myositis?
There isn’t any proven treatment. Glucorticosteroids do not work.
What malignancies are associated with polymyositis or dermatomyositis?
Lung, ovary, breast, and GI cancers
What is necrotizing myopathy?
It is not a myositis. It is an antibody mediated condition with a paucity of immune cells that can also be seen in cases of malignancy or as a paraneoplastic process.
What condition is associated with the use of statin medications?
Necrotizing myopathy - some cases of necrotizing myopathy seem to be associated with antibodies against HMGCoA reductase, possibly resulting from statin use
What is the pathology of necrotizing myopathy?
Scattered necrotic fibers without round cell infiltrate around normal fibers.
What is fasciitis with peripheral eosinophilia?
A condition where there is necrotizing myopathy that affects the fascia more than the muscle and leads to thickened skin distally but without other scleroderma-like symptoms
What is this pathology consistent with?
Polymyositis - immune infiltration and centralized nuclei
What condition is the “shawl sign” related to?
Dermatomyositis - erythema on sun exposed surfaces
What is this histology associated with?
Inclusion body myositis - apple green birifiriengence and congo red stain
Asymmetrical or distal weakness would suggest:
a) PM
b) DM
c) IBM
d) any of the above
c) IBM
The discovery of ovarian cancer 6 months into the development of weakness would suggest:
a) PM
b) DM
c) IBM
d) none of the above
a) PM or b) DM, both are tied to ovarian malignancies
Which of the following medications is most commonly associated with a necrotizing myopathy?
a) azithromycin
b) simvastatin
c) gabapentin
d) tramadol
b) simvastatin
statins are linked to necrotizing myopathy
Perifascicular atrophy is a hallmark of:
a) PM
b) DM
c) IBM
d) none of the above
b) DM - perifascicular atrophy is almost pathognomonic for DM
