MSK: 18.4-6: Skeletal Muscle, NMJ, STT Flashcards
What is dermatomyositis?
inflammation of the skin and skeletal muscle
What pathology might be simultaneously occurring in dermatomyositis?
carcinoma, esp GI
What are the s/s of dermatomyositis?
bilateral proximal weakness; purple rash of upper eyelids (heliotrope rash); malar rash; red papules on the elbows, knuckles, and knees (Grotton lesions)
How does proximal muscle weakness present?
can’t comb hair, can’t climb stairs
What are the lab findings in dermatomyositis?
increased creatinine kinase, positive ANA and anti-Jo-1 Ab, perimysial inflammation of CD4+ cells with perifasicular atrophy
What is the tx for dermatomyositis?
corticosteroids
Perimysial inflammation of muscles = ?
dermatomyositis
What is polymyositis?
an inflammatory disorder of skeletal muscle WITH NO SKIN INVOLVEMENT
What causes polymyositis?
endomysial inflammation (CD8+ T cells) with necrotic muscle fibers
Endomysial inflammation of muscles = ?
polymyositis
What is the inheritance of muscular dystrophy?
X-linked
What happens to the skeletal muscle in Muscular Dystrophy?
it’s replaced by adipose
What is the cause of Duchenne Muscular Dystrophy?
deletions of dystrophin (Duchenne’s = deletions)
What is the function of dystrophin?
an anchor molecule that anchors the ECM to skeletal muscles
What is one lab finding in Muscular Dystrophy?
elevated creatinine kinase (damage to muscle cells)
What is the problem in Becker Muscular Dystrophy?
MUTATED dystrophin (not deleted)
How does Myasthenia Gravis occur?
an antibody competes for post-synaptic ACh receptors
Weakness with increased use of the muscle occurs in ____, but this improves with rest.
Myasthenia Gravis
Anticholinesterase agents ____ Myasthenia Gravis symptoms.
improve
What are the initial s/s of Myasthenia Gravis?
drooping eyelids (ptosis) and diplopia
Myasthenia Gravis is associated with what other pathology?
thymic hyperplasia or thymoma
What is Lambert-Eaton Syndrome?
Abs against the pre-synaptic Ca++ at the NMJ
What often causes Lambert-Eaton Syndrome?
small cell carcinoma (a paraneoplastic syndrome)
What muscles are involved in Lambert-Eaton Syndrome?
proximal muscles; spares eyes
What do anticholinesterase agents do in Lambert-Eaton Syndrome?
nothing
In Lambert-Eaton Syndrome, muscle weakness ____ with use.
improves
What is the tx for Lambert-Eaton Syndrome?
resection of the cancer
What is the characteristic cell of a liposarcoma?
lipoblasts
Cardiac rhabdomyoma are associated with _____.
tuberous sclerosis
What is the characteristic cell of rhabdomyoscarcomas? What does it stain positively for?
rhabdomyoblast; desmin positive
What is the most common site for a rhabdomyoscarcoma? What about in a young girl?
head and neck; young girl = vagina
