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Neuropath > Muscles > Flashcards

Muscles Flashcards

1
Q

If you see perifascicular necrosis, what should you pick?

A

antisynthetase syndrome myositis

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2
Q

What feature is distinctive between antisynthetase syndrome myositis and dermatomyositis?

A

intranuclear actin aggregates

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3
Q

Pompe/type II glycogenosis hallmark

A

vacuolar degeneration in skeletal muscle fibers (worse in infants)

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4
Q

general concept behind dystroglycanopathies

A

Not actually a mutation in the DAG gene
usually abnormal glycosylation of alpha-dystroglycan

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5
Q

what gene has “the common mutation” in dystroglycanopathy?

A

FKRP1

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6
Q

what’s the stain for glycosylated alpha dystroglycan?

A

IIH6

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7
Q

what cell type has glycosylated alpha dystroglycan in peripheral nerve?

A

Schwann cells
(they think it’s the entry point for mycobacterium leprae)

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8
Q

where in the cell does dysferlin live?

A

sarcolemma (plasma membrane)

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9
Q

what is the function of dysferlin?

A

membrane repair

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10
Q

what are the 2 clinical syndromes/presentations for dysferlinopathies?

A
  1. limb-girdle-esque (LGMD 2B/R2)
  2. Miyoshi myopathy (distal)
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11
Q

Constellation of histopath findings for dysferlinopathy?

A
  1. total loss of Hamlet staining
  2. complement deposition (C5b-9)
  3. amyloid
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12
Q

gene & inheritance for dysferlinopathy?

A

DYSF gene
auto recessive

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13
Q

what is the antibody for dysferlin?

A

Hamlet
will be TOTALLY NEGATIVE if dz present (nonspecific sarcoplasmic staining can happen, not diagnostic of dz)
(because LGMD 2B [or not 2B])

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14
Q

what is the inflammatory component of dysferlinopathies?

A

Complement deposition (C5b-9) in myofibers

NOT increased inflammatory cells

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15
Q

You can see 2 of the dysferlinopathy histo findings in other entities. what are they?

A
  1. complement: ANO5 and LMNA
  2. amyloid: ANO5

ANO5 = anoctaminopathy
LMNA = laminopathy

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16
Q

if you have a pt presenting with chronic progressive external ophthalmoplegia (CPEO), what should your FIRST thought be?

A

mitochondrial myopathy

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17
Q

what step in the mitochondrial respiratory chain does the SDH stain rely on, and what does that tell you?

A

activity of complex II

entirely encoded by nuclear genome
so it only tells you about mitochondria quantity, NOT quality/fxn!

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18
Q

what step in the mitochondrial respiratory chain does COX rely on?

A

complex IV

some subunits are encoded by mtDNA > loss of staining

19
Q

name 2 findings you can have on EM in mitochondrial myopathies

A

paracrystalline/parking lot inclusions

hyperbranching mitochondria

20
Q

what is THE disorder of lysosomal glycogen degradation?

A

Pompe disease
aka
acid alpha-glucosidase (acid maltase) deficiency
aka
GSD II

21
Q

main diff btwn infantile & late onset Pompe dz

A

infantile: <1% enzyme activity

late: up to 30% enzyme activity

22
Q

what is the main difference in clinical presentation between Pompe and the rest of the glycogen storage myopathies?

A

Pompe presents with weakness

Others present with exercise intolerance

23
Q

most common non-Pompe glycogen storage myopathy

A

myophosphorylase deficiency
aka
GSD V
aka
McArdle dz

24
Q

what is the classic histo finding for Duchenne muscular dystrophy?

A

revertant fiber

most fibers will be negative for dystrophin, then there will be one that has expression (it’s reverted)

25
Q

what is the issue with immunostaining for Becker muscular dystrophy?

A

the stains for dystrophin (DYS1, 2, 3) do not include exons 46-50, and that is where MOST mutations causing Becker are

26
Q

how do you dx McArdle’s/myophosphorylase deficiency with IHC?

A

Loss of phosphorylase staining (duh)

27
Q

what is the structure of autophagosomes?

A

double membrane vacuoles (induction membrane)

these are delivered to lysosomes for degradation

28
Q

what are the 2 components of autophagic vacuole formation that you can stain for?

A

LC3-PE (LC3-II) > bound to membrane on inside

autophagy receptor (p62) > links cargo to LC3-PE (it’s an inductor)

29
Q

how does the autophagosome fuse with the lysosome?

A

moves along microtubule (from + to - end) to get to the center of the cell

30
Q

True or false: the autophagosome requires an alkaline pH inside of it to degrade things

A

FALSE
it requires an ACIDIC pH

(chloroquine raises the pH and impairs digestion in a lysosome)

31
Q

how do the multisystem proteinopathies manifest clinically?

A
  1. IBM
  2. ALS/FTD
  3. Paget disease of bone
32
Q

what are the protein aggregates in multisystem proteinopathies (MSP) positive for?

A

TDP-43
p62
ubiquitin
(cause it manifests as an IBM)

33
Q

What gene should you think of if you are talking about multisystem proteinopathy (MSP)?

A

VCP

34
Q

myofibrillar myopathies & their clinical issues result from disintegration of what?

A

sarcomeric Z-disc and myofibrils > abnoraml ectopic accumulation of their components (desmin, alpha B-crystallin, dystrophin, myotilin)

35
Q

what two structures NORMALLY have nemaline rods?

A

myotendinous jxn

extraocular muscle

36
Q

MC clinical thing in nemaline myopathy

A

respiratory muscle involvement

37
Q

what (VERY general) pathology has myonecrosis & regeneration with prominent satellite cells?

A

dystrophies

38
Q

what stains do you use for regenerating fibers?

A

embryonic myosin heavy chain
N-CAM/CD56

39
Q

besides total loss of dystrophin (DYS1, 2, 3) staining, what 2 other stains can help diagnose Duchenne?

A

Utrophin > upregulated, not specific

nNOS > loss (this binds to fxnal dystrophin)

40
Q

what is the mechanism of colchicine myopathy?

A

colchicine prevents microtubule polymerization, which blocks autophagosome maturation bc the autophagosome can’t get to its correct place via the microtubule tracks

41
Q

diagnostic options for this EM finding

A

curvilinear bodies

either hydroxy/chloroquine-induced or neuronal ceroid lipofuscinosis

42
Q

what is this

A

z-band streaming

can see in colchicine/vincristine toxicity, some myofibrillar myopathies, some nemaline myopathies

43
Q
A

Neuropath (6 decks)

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