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MSCT > Muscle Disease > Flashcards

Muscle Disease Flashcards

1
Q

Type I myofibers

A

High in oxidative activity, low in glycolytic capacity, red grossly (from myoglobin and mitochondrial cytochromes), contracts slowly, capable of continuous and repeated contraction

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2
Q

Type II myofibers

A

Low in oxidative activity, high in glycolytic activity, white grossly, fast contracting, cannot maintain repeated contraction

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3
Q

Neurogenic atrophy clinical clues

A

Nerve damage often with associated sensory features

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4
Q

Neurogenic atrophy histopathological features

A

Fiber type grouping, group atrophy

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5
Q

Neurogenic atrophy etiology

A

Motor nerve damage

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6
Q

Disuse/steroid atrophy clinical clues

A

Bedridden/ICU, corticosteroids (long term use), hypothyroidism

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7
Q

Disuse/steroid atrophy histopathological features

A

Type II myofiber atrophy

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8
Q

Disuse/steroid atrophy etiology

A

Atrophy of fast twitch fibers

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9
Q

Dystrophin related myopathy clinical clues

A

Childhood onset

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10
Q

Dystrophin related myopathy histopathological features

A

Myofiber size variability, necrosis, regeneration, endomysial fibrosis, fatty replacement

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11
Q

Dystrophin related myopathy etiology

A

Hereditary abnormalities of dystrophin or related proteins

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12
Q

Inflammatory myopathy clinical clues

A

Adult onset, associated rheumatologist features

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13
Q

Inflammatory myopathy histopathological features

A

Inflammation (usually T-cells), necrosis and regeneration

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14
Q

Inflammatory myopathy etiology

A

Autoimmune

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15
Q

Congenital myopathy clinical clues

A

Onset at birth, floppy baby

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16
Q

Congenital myopathy histopathological features

A

Wide variety of specific changes, inclusions, etc. (nemaline rods, central cores)

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17
Q

Congenital myopathy etiology

A

Variable

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18
Q

Channelopathies clinical clues

A

Myotonia, intermittent symptoms

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19
Q

Channelopathies histopathological features

A

May be normal

20
Q

Channelopathies etiology

A

Muscle sodium channel protein SCN4A defect

21
Q

Myopathic patterns

A

Often associated with scattered myofiber necrosis and regeneration

22
Q

Inflammatory myopathies pattern

A

Myopathic but also characterized by inflammatory infiltrates and/or intracellular inclusions

23
Q

Neuropathic changes

A

Fiber type grouping or group atrophy

24
Q

Type II myofiber atrophy from disuse

A

Due to any cause for prolonged immobilization, results in focal or generalized muscle atrophy, tends to affect type II more than type I

25
Q

Type II myofiber atrophy glucocorticoids

A

History of exposure, either exogenous or endogenous (as in Cushing syndrome), can cause muscle atrophy

26
Q

Dystrophinopathies

A

Duchenne and Becker muscular dystrophy

27
Q

Broad definition of muscular dystrophies

A

Diseases associated with the dystrophin-glycoprotein complex

28
Q

Dystrophin-glycoprotein complex function

A

Skeletal muscle membrane associated proteins involved in the mechanical stabilization and signaling interactions between the cytoskeleton, membrane, and extracellular matrix

29
Q

Duchenne muscular dystrophy clinical course

A

Evident around 5 years, wheelchair-bound by teenagers, death in early adulthood

30
Q

Clinical features of DMD

A

Gower’s sign in children, clumsiness, inability to keep up with peers, weakness begins in pelvic girdle and then shoulder, calf muscles enlarged (pseudohypertrophy), high serum creatine kinase levels early on but fall as muscle mass is lost

31
Q

Clinical features of BMD

A

Appears later in childhood or adolescence, slower and more variable progression, live well into adulthood with nearly normal life span

32
Q

Histologic changes in dystrophinpathologies

A

Ongoing myofiber necrosis and regeneration, progressive replacement of muscle tissue by fibrosis and fat, variation in myofiber size and abnormally placed internal nuclei (all of these in both BMD and DMD, but BMD is more mild), dystrophin sarcolemmal staining pattern negative (DMD) or reduced (BMD)

33
Q

Pathogenesis of dystrophinopathies

A

Loss of function mutations in dystrophin gene on the short arm of the X chromosome (Xp21)

34
Q

Congenital myopathy examples

A

Central core disease, nemaline myopathy, centronuclear myopathy

35
Q

Congenital myopathy patterns

A

Perinatal or early childhood presentation and often result in relatively static deficits

36
Q

Channelopathy patterns

A

Myotonia, relapsing episodes of hypotonic paralysis associated with abnormal serum potassium levels

37
Q

Hyperkalemic periodic paralysis

A

Mutations in gene encoding skeletal muscle sodium channel protein SCN4A, which regulates sodium entry during contraction

38
Q

Metabolic myopathy (glycogen synthesis abnormalities)

A

Detected with PAS and myophosphorylase

39
Q

Metabolic myopathy (lipid abnormalities)

A

Detected with Oil Red O

40
Q

Mitochondrial myopathies

A

Mutations in mitochondrial or nuclear genomes, usually manifest in early adulthood with proximal muscle weakness and sometimes severe involvement of ocular musculature, ragged red fibers on histology from aggregates of mitochondria

41
Q

Inflammatory myopathy examples

A

Polymyositis, dermatomyositis, inclusion body myositis

42
Q

Polymyositis

A

Autoimmune disorder associated with T-cells and increased expression of MHC class I on myofibers, endomysium damaged, responds to corticosteroids and immunosuppressive agents

43
Q

Dermatomyositis

A

Autoimmune disorder, presents with malar rash, rash on upper eyelids, red papules on elbows, knuckles, knees, on histology there is myofiber damage in a paraseptal or perifascicular pattern

44
Q

Inclusion body myositis

A

Typically in patients older than 60, morphologic hallmark is presence of rimmed vacuoles, might be a degenerative disorder of aging, myopathic changes, mononuclear cell infiltrates, endomysial fibrosis, fatty replacement, chronic and progressive course, does not respond well to immunosuppressive agents

45
Q

Toxic myopathy (thyroxine)

A

Acute or chronic proximal muscle weakness, show myofiber necrosis and regeneration, associated with thyrotoxicosis

46
Q

Toxic myopathy (ethanol)

A

After an episode of binge drinking, degree of rhabdomyolysis may be severe (can lead to acute renal failure secondary to myoglobinuria), patients present with acute muscle pain (generalized or localized to a group), myocyte swelling, necrosis, regeneration

47
Q

Toxic myopathy (drug)

A

Most commonly drugs from the statin family, affected muscles show evidence of myopathic injury usually without an inflammatory component

MSCT (28 decks)

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