Inflammatory Myopathies Flashcards
Dermatomyositis- what type of muscle weakness? Characteristic? Temporal profile? Pain? Predominance? What special screen needs to be done?
Proximal muscle weakness
Characteristic skin rash- scalp can be itchy, forearm, knuckles, etc. erythema around nail bed
Subacute temporal profile- weeks to months
Muscle pain in 50% of cases
Female predominance
Malignancy screen*
Dermatomyositis exam/basic tests
Skin
Standard, proximal muscle weakness
Elevated CK
EMG shows myopathic motor units and fibrillation
Age/gender appropriate malignancy screen- not a specific malignancy associated with dermatomyositis, but the most common malignancy for that patient.
DM treatment
Oral prednisone- 1mg/kg/day
Test/treat for prednisone side effects
Continue treatment for at least two months
Intravenous immunoglobulins with prednisone
Long-term (steroid sparing) immunosuppression with azathioprine
Inclusion body myositis- muscle weakness? Temporal profile? Pain? Characteristic problems? Predominance?
Distal finger flexor weakness and quadriceps weakness- most patients over 50 Extremely slow temporal profile- years No pain. Patients have problems swallowing Male predominance
IBM exam/basic tests
Quadriceps and distal finger flexor weakness
Other standard muscle exams are also weak
Elevated CK- extremely wide range* can almost be normal
EMG shows myopathic motor units and fibrillation
Modified barium swallow test
IBM treatment
May not treat
In uncertain cases, prednisone 1mg/kg/day
Speech and swallowing evaluation
Mobility assists, modifying home environment, gastrostomy tube
Polymyositis- muscle weakness?
Onset?
Pain?
Testing:
Standard proximal muscle weakness
Subacute onset- weeks to months
No muscle pain- may have associated connective tissue disease*
Exclusion testing mostly- acute necrotizing myopathy, viral myositis, IBM, statin-induced myopathy, cancer status (not as strongly correlated with malignancy as dermatomyositis)
PM Exam/Basic tests
Standard proximal muscle weakness
Check for joint disease
Very elevated CK levels
EMG shows myopathic motor units and fibrillation
Collaborate with immunology/rheumatology in context of connective tissue disease
PM treatment
Oral prednisone- 1mg/kg/day
Treat for 3 months and assess strength, not CK* (sometimes CK is unaffected)
Long range treatment based on: response to prednisone, connective tissue disease status, azathioprine, IVIG…
Viral myositis- Pain? Onset? Setting? Extreme cases can have:
Muscle pain predominates Rapid onset (over days) Most often in setting of viral illness Rhabdomyolysis in extreme cases
Viral Myositis exam and basic testing
Standard strength exam- strong except for pain limited elements
Elevated CK- 250,000
Sedimentation rate should be normal
Serum and urine myoglobin, renal profile
Delay all diagnostic testing for a month. Hold on EMG. Do not biopsy
VM treatment
Hydrate to reduce chance of renal failure: output of 1-2mL/kg/h
Pain control
Reduce activities
*don’t use NSAIDs because of renal complications
Maybe Tylenol
Histology patterns of general autoimmune myopathies
Not chronic inflammation- there are aggregates of lymphocytes/T cells going after muscle fiber and engulfing it. Nuclei are in the center (trying to regenerate)- regenerating muscle cell cytoplasm is more blue rather than pink- mRNA, Nissl substance, ribosomes are trying to make proteins soon, so more ribosomes are active now.
Muscle fiber is engulfed by T cells
Can set up germinal centers
Expect a nonspecific type of atrophy- type II
Dermatomyositis histology- what type of atrophy?
Where specifically?
Due to?
Inflammation tends to be around fascicle in perimysium- perifascicular atrophy
Fibers in middle of fascicle are normal sized, but ones on the outside of it are atrophied
Pattern of atrophy not due to nonspecific inflammatory or toxins- it is due to vascular etiology
These patients have BV’s on outside of fascicles that have microthrombin in them- C3/5b complement and platelets and fibrin that occlude the vesicles: ischemic pattern of atrophy
IBM histology
Inflammation like polymyositis
Some fibers are very big, some are clearly atrophic
What WAS a single fiber splits to form daughter fibers- also seen in MD sometimes
Rimmed vacuole- empty space appearance in middle of fiber, rimmed with basophilic granules
Mineralized membrane debri that can become calcified
Rimmed vacuoles contain lysosomes and membrane debri- doesn’t give you a clue of the cause of the disease
Sometimes have amyloid material accumulation
