Pathoma: Skeletal Muscle, Neuromuscular Junction, and STT Flashcards
Although the etiology of dermatomyositis is not known, there is a high-yield association between dermatomyositis and ______________.
carcinoma, particularly gastric carcinoma
What are the signs and symptoms of dermatomyositis?
- Malar rash
- Heliotrope rash
- Proximal muscle weakness (“I can’t lift my arms up to comb my hair” or difficult climbing stairs)
- Papular rash on elbow, knuckles, and knees
What are the laboratory/histologic findings associated with dermatomyositis?
- ANA and anti-Jo-1 antibodies
- Elevated CK (because of myopathy)
- Perimysial inflammation (CD4+) with fascicular atrophy
What are the three layers of fascia around a muscle?
- Outermost: epimysium
- Middle: perimysium
- Innermost: endomysium
Differentiate the inflammation of polymyositis from dermatomyositis.
•Dermatomyositis:
- CD4+ cells
- Perimysial
•Polymyositis:
- CD8+ cells
- Endomysial
(Good mnemonic: the perimysium is closer to the DERMis, so it makes sense that dermatomyositis affects the outer of the two muscle fascia layers.)
What are the presenting signs and symptoms of polymyositis?
- Proximal muscle weakness
- No skin involvement
- Skeletal muscle necrosis (from CD8+ cells attacking the endomysium)
Duchenne’s X-linked muscular dystrophy is due to ___________ of the dystrophin gene.
out-of-frame deletions
The classic histologic hallmark of muscular dystrophy is ___________________.
fibrofatty replacement of muscle
Becker’s is like Duchenne’s, but because it results from ______________, it has a milder phenotype.
in-frame deletions or mutations
Give a quick rundown on myasthenia gravis.
- Results from antibodies to the acetylcholine receptor on postsynaptic muscle cells
- Initial firings of the NMJ will produce normal-strength action potentials, but due to the depletion of neurotransmitter stores weakness will develop
- Often presents with thymoma *****
- Treated with acetylcholinesterase inhibitors
- More common in women
- Classically involves ptosis or diplopia
- Symptoms improve with rest *******
True or false: thymomas are removed to prevent malignant invasion.
False. Thymomas are benign. They are removed because their removal usually cures myasthenia gravis.
Lambert-Eaton myasthenic syndrome (LEMS) most often results from _______________.
small cell carcinoma of the lung
Give a quick rundown on LEMS.
- Results from antibodies to presynaptic calcium channels
- Usually involves the proximal muscles and spares the eyes
- Symptoms improve with activity
- Usually treated with removal of the causative tumor
_______________ cells are characteristic of liposarcoma.
Lipoblast
True or false: rhabdomyosarcoma is associated with tuberous sclerosis.
False. Cardiac rhabdomyomas (not sarcomas) are associated with TS.
