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MSK II Midterm > Peripheral Nerve and Skeletal Muscle Pathology > Flashcards

Peripheral Nerve and Skeletal Muscle Pathology Flashcards

1
Q

Guillain-Barre Syndrome (acute inflammatory demyelinating polyneuropathy)

A
  • life threatening resp paralysis
  • weakness beginning in distal limbs that rapidly advanes to affect prox muscle function
  • Inflammation and demyelination of spinal nerve roots and peripheral nerves
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2
Q

What is the pathogenesis of guillain-barre thought to be?

A

-an acute onset immune mediated demyelinating neuropathy

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3
Q

What precedes guillain-barre syndrome?

A

-an acute, influenza-like illness

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4
Q

What is the most prominent lesion in guillain barre?

A

-segmental demyelination affecting peripheral nerves is the most prominent lesion

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5
Q

clinical features of guillain barre?

A
  • ascending paralysis and areflexia

- CSF ptn levels are elevated

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6
Q

tx for guilain barre

A

-plasmapheresis and IV immunoglobulin appear to be beneficial

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7
Q

Chronic Inflammatory Demyelinating poly(radiculo)neuropathy

A

-mot common chronic acquired inflammatory peripheral neuropathy, charcterized by symmetrical mixed sensorimotor polyneuropathy that persists for 2 months or more

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8
Q

Neuropathy associated with systemic autoimmune diseases

A
  • RA
  • SLE
  • Sjogren
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9
Q

Lepromatous Leprosy

A
  • schwann cells are invaded by mycobacterium leprae
  • loss of sensation contributes to injury
  • thus, large traumatic ulcers may develop
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10
Q

Tuberculoid leprosy

A
  • active cell mediated immune response to M leprae

- dermal nodules containing granulomatous inflammation

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11
Q

lyme disease

A
  • polyradiculopathy

- unilateral or bilateral facial nerve palsies

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12
Q

HIV/AIDS

A

-later stages are associated with a distal sensory neuropathy that is often painful

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13
Q

Diphtheria

A

-developing world
-peripheral nerve dysfunction results from the effects of diphtheria exotoxin
-

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14
Q

Varicella-Zoster Virus

A
  • one of the most common viral infections of peripheral nervous system
  • latent infection persists within neurons of sensory ganglia
  • gets transported along the sensory nerves to the skin
  • there, it infects keratinocytes, leading to a painful, vesicular skin eruption (shingles) in a distribution that follows sensory dermatomes
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15
Q

What is the most common cause of peripheral neuropathy?

A
  • diabetes

- ascending distal symmetric

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16
Q

Uremic neuropathy

A
  • renal failure
  • axonal degeneration
  • regeneration and recovery are common after dialysis
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17
Q

What is the most notorious cause of toxic neuropathies?

A

-chemotherapeutic agents

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18
Q

POEMS syndrome

A
  • polyneuropathy
  • organomegaly
  • endocrinopathy
  • monoclonal gammopathy
  • skin changes
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19
Q

Hereditary motor and sensory neuropathies/Charcot Marie tooth disease (CMT)

A
  • most common inherited peripheral neuropathy

- schwann cell hyperplasia and onion bulb formation

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20
Q

What chromosome is duplicated in CMT1A?

A
  • 17
  • PMP22
  • 2nd decade of life
  • slowly progressive distal demyelinating motor and sensory nueropathy
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21
Q

CMT1B

A

-caused by mutation in the myelin protein zero gene and accounts for about 9% of genetically

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22
Q

What kind of injury is found in CMT2?

A

-axonal rather than demyelinating injury

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23
Q

Hereditary neuropathy with pressure palsy

A
  • deletion of gene encoding PMP22
  • transient motor and sensory mononeruopathies that are triggered by compression of individual nerves at sites that are prone to entrapment
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24
Q

What is the characteristic morphologic feature for hereditary neuropathy with pressure palsy?

A

-swolen, bulbous myelin sheaths at the end of internodes (tomaculi)

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25
Q

Familial amyloid polyneuropathies

A
  • characterized by amyloid deposition within peripheral nerves
  • mutation of the the transthyretin gene
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26
Q

How do diseases of the NM junction present?

A

-with painless weakness

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27
Q

Myasthenia gravis

A

Autoantibodies against the postsynaptic Ach receptor at the NM junction

  • more commonly seen in women
  • competitive inhibition
  • bimodal age distribution
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28
Q

what else will there be in a mysthenia gravis patient?

A
  • thymic abnormalities

- thymectomy improves sx

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29
Q

clinical features of mysathenia gravis

A
  • that worsens with use and IMPROVES WITH REST
  • classically involves the eyes, leading to ptosis and diplopia
  • sx improve with anticholinesterase agents
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30
Q

Lambert-Eaton myasthenic syndrome

A
  • antibodies against presynaptic Ca2+ channels of the nm junction
  • arises as a paraneoplastic syndrome, most commonly due to SMALL CELL CARCINOMA OF THE LUNG
  • leads to impaired Ach release
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31
Q

what is required for Ach release?

A

-firing of presynaptic calcium channels

32
Q

Clinical features of lambert-eaton syndrome

A
  • pros muscle weakness that IMPROVES WITH USE
  • eyes are usually spared
  • Ach agents do not improve symptoms.. makes sense bc Ach isn’t the issue
  • resolves with resection of the cancer
33
Q

tx for lambert eaton

A

-drugs that increase AcH rlease by depolarizing synaptic membranes

34
Q

What mutation will be there is congenital myasthenic syndromes?

A

-most commonly LOF in the gene encoding the e subunit of the AcH receptor

35
Q

Botulinism

A
  • C botulinum

- blocking the release of Ach from presynaptic neurons

36
Q

what is a common name for muscle relaxants that block AcH receptors, resulting in flaccid paralysis?

A
  • Curare

- used as poison on arrow tips

37
Q

Dermatomyositis

A
  • Inflammatory disorder of the skin and skeletal muscle

- unknown etiology

38
Q

clinical features of dermatomyositis

A
  • bilateral prox muscle weakness; distal involvement can develop late in disease
  • rash of upper eyelids (heliotrope rash); malar rash may also be seen
  • red papules on elbows, knuckles, and knees (gottron papules)
39
Q

lab findings for dermatomyositis

A
  • increased creatine kinase
  • positive ANA and anti-Jo-1-antibody
  • perimysial inflammation with perifascicular atrophy on biopsy
40
Q

tx for dermatomyositis

A

-steroids

41
Q

What other antibodies besides anti-Jo-1 antibodies would we find in dermatomyositis?

A
  • anti Mi2 antibodies: prominent gottron papules and heliotrope rash
  • anti-P155/P140 antibodies: for paraneoplastic and juvenile cases
  • anti Jo-1 will have interstitial lung disease and “mechanics hands”
42
Q

What is the key morphologic feature of dermatomyositis?

A
  • perfascicular atrophy… characteristic of dermatomyositis

- polymyositis is endomysial

43
Q

What is the most common inflammatory myopathy in children?

A

-dermatomyositis

44
Q

Polymyositis

A
  • inflammatory disorder of skeletal muscle
  • resembles dermatomyositis clinically, but skin is NOT involved
  • endomysial inflammation (CD8+ T cells) with necrotic muscle fibers is seen on biopsy
  • adult onset
  • symmetric proximal muscle involvement
45
Q

What is believed to play a major role in dermatomyositis but not polymyositis?

A

-vascular injury

46
Q

Inclusion body myositis

A
  • late adulthood
  • most common inflammatory myopathy in pts older than 65
  • quadriceps and distal upper extremity muscle weakness
  • most myositis associated autoantibodies are absent
  • anti cN1A
  • doesnt’ respond to steroids
47
Q

What are the leading culprits of toxic myopathies?

A
  • statins

- myopathy is the most common complication of statins

48
Q

X-linked muscular dystrophy

A
  • degeneative disorder characterized by muscle wasting and replacement of skeleatl muscel by adipose tissue
  • due to defects in dystrophin gene
49
Q

what is dystrophin important for?

A

-anchoring the muscle cytoskeleton to the ECM

50
Q

Duchenne muscular dystrophy

A
  • due to deletion of dystrophin
  • presents as prox muscle weakness at 1 year of age, progresses to involve distal muscles
  • calf pseudohypertrophy is characteristic
  • serum creatine kinase is elevated
51
Q

What does death result from in Duchenne?

A
  • cardiac or respiratory failure

- the myocardium is commonly involved

52
Q

Becker muscular dystrophy

A
  • due to mutated dystrophin
  • clinically results in milder disease
  • so, it’s not totally deleted
53
Q

where is the dystrophin gene?

A

-on the X chromosome

54
Q

what will we see on IF for Duchenne and Becker

A
  • Duchenne: absence of normal sarcolemmal staining pattern

- Becker: reduced staining

55
Q

clinical presentation for duchenne?

A
  • clumbsy boys who can’t keep up with their peers

- beckerpresents in later childhood

56
Q

Myotonic dystrophy

A

-auto dominant multisystem disorder associated with skeletal muscle weakness, cataracts, endocrinopathy, and cardiomyopathy

57
Q

pathogenesis of myotonic dystrophy

A

-expansions of CTG triplets in region of DMPK gene

58
Q

Emery-Dreifuss Muscular dystropy

A
  • caused by mutation sin genes that encode nuclear laminal proteins
  • triad of slowly progressive humeroperoneal weakness, cardiomyopathy associated with conduction defects, and early contractures of the achilles tendon, spine, and elbows
  • inner face of nuclear membrane
59
Q

Fascioscapulohumeral dystrophy

A
  • characteristic pattern of muscle inovlvement that includes prominent weakness of facial muscles and muscles of the shoulder girdle
  • DUX4 overexpression on chrom 4
60
Q

Limb-Girdle muscular dystrophy

A

-characterized by muscle weakness that preferentially involves proximal muscle groups

61
Q

Carnitine palmitoyltransferase 2 deficiency

A
  • most common disorder of lipid metabolism to cause episodic muscle damage with exercise or fasting
  • impaired transport of free fatty acids into mitochondria
62
Q

Myophosphorylase deficiency (McArdle disease)

A
  • common glycogen storage disease

- episodic muscle damage with exercise

63
Q

acid maltase deficiency

A
  • impaired lysosomal conversion of glycogen to glucose
  • glycogen accumulates within lysosomes
  • severe form results in generalized glyogenosis of infancy… Pompe disease
64
Q

mitochondrial myopathies

A
  • impair the ability of mitochondria to generate ATP
  • involvement of extraocular eye muscles in common … good clue for dx
  • chronic progressive external opthalmoplegia is a common feature
  • “ragged red fibers”: abnormal aggregates of mitochondria
65
Q

Spinal muscular atrophy mutation?

A
  • auto recessive

- LOF in SMN1 gene

66
Q

Schwannomas

A
  • benign tumors that exhibit schwann cell differentiation and often arise directly from peripheral nerves
  • component of NF2
  • chromosom 22: merlin on the NGS gene
  • immunoreactivity for S-100
67
Q

What are Verocay bodies?

A
  • in schwannomas

- nuclear free zones that lie between the regions of nuclear palisading

68
Q

Neurofibromas

A
  • benign nere sheath tumors that are more heterogenous in composition than schwannomas
  • only the schwann cells in this disease show complete los of NF1 gene product
  • bland Schwann cells admixed with stromal cells such as mast cells, perineurial cells, CD34+ spindle cells, and fibroblasts
69
Q

what is the NF1 gene product?

A
  • neurofibromin

- suppresses RAS activity by stimulating GTPase

70
Q

Malignant peripheral nerve sheath tumors (MPNSTs)

A
  • high grade tumors
  • arise in NF1 (1/2 of them do)
  • pporly defined tumor masses that frequently infiltrate along the axis of the parent nerve and ivade adjacent soft tissues
  • divergent differentiation
71
Q

Which MPNST has rhabdomyoblastic morphology?

A

-Triton tumor

72
Q

Neurofibromatosis 1

A
  • pigmented nodules of the irs
  • cutaneous hyperpigmented macules (cafe au laits pots
  • LOF in NF1 on chrom 17: encodes neurofibromin
  • In the absence of NF-1, RAS remains trapped in its active state
  • auto dominant
73
Q

Neurofibromatosis 2

A
  • auto dominant
  • bilateral 8th nerve schwannomas
  • multiple meningioma
  • much less common that NF1
  • NF2 gene product: merlin
74
Q

What are the 3 kinds of neurofibromas

A
  • Superficial cutaneous neurofibromas: pedunculated nodules…if multiple.. NF1
  • Diffuse neurofibromas: large plaquelike elevation of skin… NF1
  • Plexiform neurofibromas: NF1 associated… bag of worms
75
Q

Where do most schwannomas occur?

A
  • at the CPA, where they are attached to the vestibular branch of the 8th nerve
  • that is where the tinnitus and hearing loss come from
  • “acoustic neuroma”: not from 8ht nerve…. not a neuroma…. idiots

MSK II Midterm (15 decks)

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