Muscles Flashcards
(43 cards)
If you see perifascicular necrosis, what should you pick?
antisynthetase syndrome myositis
What feature is distinctive between antisynthetase syndrome myositis and dermatomyositis?
intranuclear actin aggregates
Pompe/type II glycogenosis hallmark
vacuolar degeneration in skeletal muscle fibers (worse in infants)
general concept behind dystroglycanopathies
Not actually a mutation in the DAG gene
usually abnormal glycosylation of alpha-dystroglycan
what gene has “the common mutation” in dystroglycanopathy?
FKRP1
what’s the stain for glycosylated alpha dystroglycan?
IIH6
what cell type has glycosylated alpha dystroglycan in peripheral nerve?
Schwann cells
(they think it’s the entry point for mycobacterium leprae)
where in the cell does dysferlin live?
sarcolemma (plasma membrane)
what is the function of dysferlin?
membrane repair
what are the 2 clinical syndromes/presentations for dysferlinopathies?
- limb-girdle-esque (LGMD 2B/R2)
- Miyoshi myopathy (distal)
Constellation of histopath findings for dysferlinopathy?
- total loss of Hamlet staining
- complement deposition (C5b-9)
- amyloid
gene & inheritance for dysferlinopathy?
DYSF gene
auto recessive
what is the antibody for dysferlin?
Hamlet
will be TOTALLY NEGATIVE if dz present (nonspecific sarcoplasmic staining can happen, not diagnostic of dz)
(because LGMD 2B [or not 2B])
what is the inflammatory component of dysferlinopathies?
Complement deposition (C5b-9) in myofibers
NOT increased inflammatory cells
You can see 2 of the dysferlinopathy histo findings in other entities. what are they?
- complement: ANO5 and LMNA
- amyloid: ANO5
ANO5 = anoctaminopathy
LMNA = laminopathy
if you have a pt presenting with chronic progressive external ophthalmoplegia (CPEO), what should your FIRST thought be?
mitochondrial myopathy
what step in the mitochondrial respiratory chain does the SDH stain rely on, and what does that tell you?
activity of complex II
entirely encoded by nuclear genome
so it only tells you about mitochondria quantity, NOT quality/fxn!
what step in the mitochondrial respiratory chain does COX rely on?
complex IV
some subunits are encoded by mtDNA > loss of staining
name 2 findings you can have on EM in mitochondrial myopathies
paracrystalline/parking lot inclusions
hyperbranching mitochondria
what is THE disorder of lysosomal glycogen degradation?
Pompe disease
aka
acid alpha-glucosidase (acid maltase) deficiency
aka
GSD II
main diff btwn infantile & late onset Pompe dz
infantile: <1% enzyme activity
late: up to 30% enzyme activity
what is the main difference in clinical presentation between Pompe and the rest of the glycogen storage myopathies?
Pompe presents with weakness
Others present with exercise intolerance
most common non-Pompe glycogen storage myopathy
myophosphorylase deficiency
aka
GSD V
aka
McArdle dz
what is the classic histo finding for Duchenne muscular dystrophy?
revertant fiber
most fibers will be negative for dystrophin, then there will be one that has expression (it’s reverted)
