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Muscle Disorders Flashcards

1
Q

What are the 5 questions you should include in your history for a patient with a muscle disease?

A
  1. What are the symptoms?
  2. What is the temporal course?
  3. Is there a family history of muscle disease?
  4. Are there provocative factors?
  5. Is there a pattern for symptoms?
  6. Are other symptoms involved?
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2
Q

Wha is the most common pattern of acquired muscle weakness?

A

Proximal

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3
Q

What are the “negative” symptoms of muscle disease?

A

weakness

fatigue

atrophy

exercise intolerance

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4
Q

What are the “positive” symptoms of muscle disease (7) ?

A

myalgia

cramps

hypertrophy

contractures

stiffness

myotonia

myoglobinuria

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5
Q

What are the 3 components to a muscle examination? Describe the specific aspects of each.

A
  1. Look
    1. atrophy, pseudohypertrophy, fasciculation
  2. Touch
    1. palpate for tenderness, check muscle tone
  3. Engage
    1. test power (0-5)
      1. weakness due to pain, fatigue, decreased effort?
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6
Q

What special test is being performed in the provided image?

What are 2 other tests for the same pathology?

A

Percussion Myotonia

percuss thenar emminence & there is an abnormal contraction of abductor pollicis brevis

Can also test: have them grip hand (+ = delay in opening); close eyes (+ = delay in opening)

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7
Q

Percussion myotonia is seen in what two types of diseases?

A

myotonic dystrophy & channelopathies

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8
Q

What change in reflexes do you see in muscle disease?

A

reflexes are never increased

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9
Q

The presence of what additional symptoms indicate that a primary myopathy is unlikely?

A

sensory, bowel, or bladder symptoms

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10
Q

What is the most important diagnostic test to perform when muscle disease is suspected?

A

Creatinine phosphokinase

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11
Q

Is CPK usually elevated or depressed in muscle disease?

A

elevated

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12
Q

CPK is markedly elevated in what 4 muscle diseases?

A

duschenne/Becker dystrophy

inflammatory myopathies

hypothyroid myopathy

rhabdomyolysis

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13
Q

CPK is low/normal in what 4 muscle diseases?

A

dermatomyositis

steroid-induced myopathy

thyrotoxic myopathy

hyperparathyroidism

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14
Q

What are the 4 major causes of Rhabdomyolysis?

A

neuroleptic malignant syndrome - antipsychotics

malignant hyperthermia- anesthesia

crush or blast injuries; muscle ischemia

statins (rare)

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15
Q

What thyroid conditions can lead to acquired muscle diseases & what is the general CK associated with each?

A
  • Hypothyroidism- myxedema (CK 10-100x)
  • Hyperthyroidism- thyrotoxic myopathy (CK low/normal)
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16
Q

What muscle issues do you see in hypoparathyroidism? Hyperparathyroidism?

A
  • Hypoparathyroidism: tetany
  • Hyperparathyroidism: proximal myopathy
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17
Q

How will corticosteroid induced myopathy show up on biopsy?

A

type 2 fiber atrophy

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18
Q

What exogenous steroid dosing should you start to be concerned about induced myopathy?

A

>30mg/day x weeks/months

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19
Q

What is the most common type of electrolyte imbalance that can lead to myopathy?

A

hypokalemia

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20
Q

If a person is on a statin, what additional medications drastically increases the chances of developing rhabdomyolysis?

A

calcium channel blocker

cyclosporine

gemfibrozil

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21
Q

Why do statins cause myopathy?

A

they decrease mevalonate - a terpene / steroid precursor

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22
Q

10% of patients on statins experience what muscle-related side effects?

A

myalgia/cramps

rhabdomyolysis is RARE (0.1%)

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23
Q

What genetic factors predispose individuals to statin-induced muscle disease?

A
  • 2% pop is homozygous for SNP
  • rare autoimmune HMG-CoA Reductase
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24
Q

What are the 4 substance that most commonly cause toxic myopathies?

A

EtOH, cocaine, colchicine, penicillamine

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25
Q

Antipsychotics can induce what syndrome that includes muscle disease? What are the symptoms of this syndrome?

A

Neuroleptic malignant syndrome

fever, muscular rigidity, rhabdomyolysis, delirium, death (5-10%)

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26
Q

What is the cause of Malignant Hyperthermia?

A

autosomal dominant ryanodine receptor mutation (chromosome 19) - exposure to depolarizing muscle relaxants (succinylcholine) or inhaled anesthetics (halothane, sevoflurane, desflurane)

this causes increased calcium release from sarcoplasmic reticulum

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27
Q

What are the symptoms seen in Malignant Hyperthermia?

A

muscle rigidity, hyperthermia, cardiac arrhythmias, CK elevation, metabolic acidosis, myoglobinuria

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28
Q

What is the treatment for malignant hyperthermia?

A

dantrolene

prevents release of calcium

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29
Q

What demographics of people are affected by criticla illness myopathy?

A

patients ventilated in ICU who are exposed to prolonged disuse and neuromuscular blocking agents

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30
Q

What are the symptoms of critical illness myopathy? muscle biopsy?

A

proximal flaccid weakness (usually not severe)

CK elevation

biopsy: loss of reactivity for myosin ATPase activity in type 1 fibers more than type 2 fibers

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31
Q

How can you tell the difference between steroid-induced myopathy vs critical illness myopathy:

biopsy?

causative drug?

distribution?

A
  • Steroid-induced myopathy
    • biopsy: type 2 fiber atrophy
    • causative drug: prednisone > 30mg/day
    • distribution: spares bulbar/facial and distal muscles
  • Critical Illness Myopathy
    • biopsy: type 1 atrophy > type 2 atrophy
    • causative drug: neuromuscular blocking agents + disuse
    • distribution: proximal
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32
Q

What viral infections can cause localized myositis?

A

influenza A & B, HIV

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33
Q

What bacterial infections can cause localized myositis?

A

streprococci, MRSA

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34
Q

What parasitic infections can cause localized myositis?

A

trichinosis

cysticercosis

toxoplasmosis

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35
Q

What is the classic clinical picture of a patient with dermatomyositis?

A

female with subacute, symmetric, proximal > distal weakness

(dysphasia/dysphagia, polyarthritis, interstitial lung disease)

often associated with cancer or other autoimmune conditions

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36
Q

What elevated lab values would you expect to see in a patient with dermatomyositis? Antibodies?

A

CK

LDH

aminotransferase

30% (+) myositis antibodies

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37
Q

Dermatomyositis is what type of condition?

A

microangiopathy directed against intramuscular blood vessels

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38
Q

What type of findings are seen in a muscle biopsy of a patient with dermatomyositis?

A

perifascicular atrophy

vasculitic changes

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39
Q

What is the treatment for dermatomyositis?

A

immunosuppression with steroids → then progress to steroid sparing agents (ie methotrexate/azathioprine)

40
Q

What skin signs are associated with dermatomyositis? Are these always present?

A

heliotrope rash, V-sign, shawl sign, Gottron’s papules

no- may not manifest until years after weakness starts

41
Q

Initially dermatomyositis can look very similar to what condition? How can you distinguish?

A

polymyositis

distinguish via muscle biopsy (poly: cellular infiltration within the fascicle; dermato: perifascicular)

42
Q

What is the classic clinical picture of a patient with polymyositis?

A

female with subacute, symmetric, proximal > distal weakness

(dysphasia/dysphagia, polyarthritis, interstitial lung disease)

often associated with cancer or other autoimmune conditions

43
Q

What elevated lab values would you expect to see in a patient with polymyositis? Antibodies?

A

CK

LDH

aminotransferase

30% (+) myositis antibodies

44
Q

What type of findings are seen in a muscle biopsy of a patient with polymyositis?

A

Cellular infiltration within the fascicle; CD8+ mononuclear

45
Q

How does polymyositis differ from polymyalgia rheumatica?

A

polymyalgia rheumatica has pain but no weakness

46
Q

What is the treatment for polymyositis?

A

Immunosuppression

47
Q

What is the most common acquired muscle disorder over age 50?

A

Inclusion Body Myositis

48
Q

What is the common clinical picture of a patient with inclusion body myositis?

A

Male over the age of 50 with asymmetric progressive weakness of the finger flexors, wrist flexors, knee extensors and ankle dorsiflexors

medial/lateral anterior thigh atrophy

dysphasia

associated with other autoimmune conditions

49
Q

What CK & serum lab values are seen in Inclusion Body Myositis?

A

CK: mild / no elevation

Serum: cytosolic 5’-nucleotidase 1A abs in 60% (worse prognosis)

50
Q

What type of findings are seen in a muscle biopsy of a patient with Inclusion body Myositis?

A

Rimmed vacoules

51
Q

What is the treatment for Inclusion body myositis?

A

minimal response to immunotherapy

52
Q

What is dystrophin & what gene is it encoded by?

A

cytoplasmic protein that connects muscle fiber cytoskeleton to surrounding extracellular matrix through the cell membrane

DMD gene

53
Q

What is the most common dystrophinopathy?

A

Duchenne muscular dystrophy

54
Q

Duchenne Muscular Dystrophy shows what type of inheritance pattern?

A

X-linked recessive

55
Q

Describe the progression of a patient with Duchenne Muscular Dystrophy.

A
  • 3-6yr
    • wide based, wadded gait
    • toe walking
    • trouble running/walking
    • neck weakness
    • CK 50-100x nl
  • 10yr
    • cannot climb stairs
    • Gowers’ sign
  • 12yr
    • confined to wheelchair
  • Death by approx 20yr
56
Q

If a patient is still ambulatory beyond 16th birthday, they have what type of muscular dystrophy?

A

Becker’s Muscular Dystrophy

57
Q

What are the classic exam finding seen in patients with Duchenne Muscular Dystrophy?

A

calf pseudohypertrophy (fatty infiltration)

low reflexes

58
Q

What sign is shown in the provided image? It is indicative of what pathology?

A

Gowers’ Sign

Duchenne Muscular Dystrophy

59
Q

What is the treatment plan for patients with Duchenne Muscular Dystrophy?

A

Multidisciplinary approach

Corticosteroids should be offered to all boys with DMD (deflazacourt)- prolongs walking, reduces falls, improves respiration, decreases scoliosis, improves cardiac & cognitive function

60
Q

What is the recessive pattern of Becker Muscular Dystrophy?

A

X-linked recessive (Xp21)

61
Q

What is the onset & presentation of Becker Muscular Dystrophy?

CK value?

A

Similar to DMD but milder phenotype (also have calf pseudohypertrophy)- presents later

onset: 5-6 yr or 5th-6th decade (older onset = slower progression)

CK = 20-80x normal

62
Q

What is the typical life-expectancy of a patient with Becker Muscular Dystrophy?

A

4th-5th decade

63
Q

Becker Muscular Dystrophy is an important differential in what seemingly unrelated condition?

A

adult onset idiopathic dilated cardiomyopathy

64
Q

What are the features seen in Emery-Dreifuss Muscular dystrophy?

A
  • early contractures
  • no pseudohypertrophy
  • humeroperoneal weakness in childhood
  • cardiac arrhythmia/conduction block
65
Q

What is the cause of Facioscapulohumeral Muscular Dystrophy?

Inheritance Pattern?

A

Chromosome 4

when D4Z4 tandem repeat is truncated to 10 or less, this induces DUX4 gene transcript

Autosomal dominant (30% sporadic)

66
Q

What is the typical presentation & progression of a patient with Facioscapulohumeral Muscular Dystrophy?

A

M=F

onset teens- symptoms usually fully manifested by age 20yr

(descending weakness)= facial (eye/lip) → scapular → proximal arm → leg

spares the deltoid

67
Q

Limb-Girdle Muscular Dystrophy Group has what type of inheritance pattern?

A

autosomal recessive

68
Q

What is the most common type of Limb-Girdle Muscular Dystrophy Group? Onset?

A

Calpainopathy - 75% onset before 20 yr

69
Q

What are the symptoms seen in Limb-Girdle Muscular Dystrophy Group? Treatment?

A
  • Symmetric proximal leg weakness > shoulder-girdle
    • very severe hip extensor, hip adductor, knee flexor weakness
    • weakness of deltoid (late)
  • Scapular winging, abdominal laxity
  • generally spaces facial muscles
  • normal life span

No disease modifying therapy

70
Q

What is the most common muscular dystrophy in adults?

A

myotonic dystrophy (F=M)

71
Q

What is the inheritance pattern of Type 1 & Type 2 Myotnic Dystrophy? Specific mutations?

A
  • Type 1:
    • autosomal dominant
    • Chromosome 19
      • unstable CTG repeat (anticipation- phenotype shows up earlier in successive generations)
  • Type 2:
    • autosomal dominant
    • Chromosome 3
      • CCTG (no anticipation)
72
Q

Describe the difference in presentation between Type 1 & Type 2 Myotonic Dystrophy?

A
  • Type 1:
    • Distal weakness
      • finger & wrist extensor → neck/jaw/facial
      • “Hatchet face” w/ myotonia on exam (grip/percussion/eyelid)
    • cardiorespiratory involvement
    • insulin resistance
    • Death by 50
  • Type 2:
    • proximal weakness:
      • legs/mild neck flexor weakness
      • mild / no myotonia
    • lung spared
    • les cardiac involvement
    • normal lifespan
73
Q

What condition is characteristic by the provided image?

A

Type 1 Myotonic Dystrophy

“Hatchet Face”

74
Q

What is the cause of Pompe Disease (GSD Type II)? Inheritance pattern?

A

Autosomal Recessive

Chromosome 17 - mutation with acid maltase (acid-alpha glucosidase)

glycogen is not converted to glucose → abnormal glycogen accumulation in lysosomes / cytoplasm

75
Q

What is the difference in Pompe Disease presentation in infants vs. adults?

A
  • Infants (severe)
    • hypotonia, enlarged tongue, cardiomegaly, hepatomegaly
    • die age 1-2yr
  • Adults (milder)
    • pelvic > shoulder weakness, abdominal/diaphragm weakness
76
Q

What abnormal lab tests would you expect to see in a patient with Pompe Disease (GSD Type II)?

A
  • CK: elevated
  • EMG: irritable myopathy, myotonia
  • Pulmonary testing: FVC supine
  • Acid maltase activity: abnormal
77
Q

Treatment of Pompe Disease (GSD Type II)?

A

alglucosidase alpha (myozyme)

78
Q

Which GSD is static vs dynamic?

A

Static: Pompe Disease (GSD Type II) - weak all the time

Dynamic: McArdle Disease (GSD Type V)

79
Q

What is the cause of McArdle Disease (GSD Type V)? Inheritance pattern?

A

autosomal recessive

mutation in PYGM gene - cannot break down glycogen into glucose-1-phosphate

80
Q

What is the typical onset of McArdle Disease (GSD V)? Symptoms? Lab values?

A
  • onset: 1st decade / maybe not until 20s/30s
  • symptoms:
    • exercise induced cramps/myalgias with second wind phenomenon
    • myoglobinuri & muscle contracture with sustained exercise
    • CK elevation ~1000, sustained 1-2 months
81
Q

What is the treatment for McArdle Disease (GSD V)?

A

creatine, carbohydrate rich diet, vitamin B6

avoid excessive or intense exercise; have a candy bar on hand

avoid general anesthesia

82
Q

What is the causes of Carnitine Palmitoyltransferase II Deficiency? Inheritance pattern?

A

autosomal recessive

CPT II is an inner mitochondrial membrane protein; defect causes impaired beta oxidation - disorder of lipid metabolism

83
Q

What is the typical age of onset for Carnitine Palmitoyltransferase II Deficiency? Symptoms?

A
  • Onset: 20-30s
  • Symptoms: Recurrent myoglobinuria
    • myalgias/cramps after exercise
    • do NOT see second wind phenomenon
    • normal CK between exercise periods
84
Q

Carnitine Palmitoyltransferase II Deficiency is seen most commonly in what situations? Treatment?

A

gradual onset / resolutions of cramps; with prolonged exercise

seen more with fasting, infection, low carb or high fat diet

avoid valproic acid

85
Q

What is the most common cause of recurrent myoglobinuria in adults?

A

Carnitine Palmitoyltransferase II Deficiency

86
Q

Inheritance pattern of hypokalemic periodic paralysis? Cause?

A

autosomal dominant

voltage-gated calcium or ligand-gated sodium channel

(66% have CACNA1S mutation; SCN4A mutation less common)

87
Q

Typical age of onset for hypokalemic periodic paralysis? Symptoms? Lab findings?

A
  • Onset
    • 10-20yrs - remits after 35 yrs of age (may have limb girdle weakness later in life)
  • Symptoms:
    • long episodes of paralysis (hours to days)- 7/9 times per month
      • paralysis usually spares the ocular, bulbar & respiratory muscles
  • Lab findings:
    • serum K < 3 mEq/L; transient CK elevation
    • Exercise EMG: increased cAMP amplitude without electrical myotonia
88
Q

What are the triggers for Hypokalemic periodic paralysis?

A

intake high carb meal, EtOh, cold, resting after exercise, stress

89
Q

What is the treatment for Hypokalemic periodic paralysis?

A

KCl

carbonic anhydrase inhibitors (acetazolamide) for prevention

avoid carbohydrate meals & strenuous exercise

mild exercise may abort an attack

90
Q

What is the cause of hyperkalemic periodic paralysis? Inheritance pattern?

A

autosomal dominant channelopathy

voltage-gated sodium channel mutation (SCN4A)

91
Q

Typical age of onset for hyperkalemic periodic paralysis? Symptoms? Lab findings?

A
  • onset:
    • 5-15 yr; remits after 20 yr of age
  • Symptoms:
    • Brief episodes of weakness (minutes to hours) involving proximal muscles - ~15 x / month
  • Lab:
    • serum K > 5.0 mEq/L, not always
    • Exercise EMG: increased cAMP amplitude with electrical myotonia
92
Q

What are the triggers for Hyperkalemic periodic paralysis?

A

potassium rich foods, fasting, cold, rest after exercise

93
Q

What is the treatment for Hyperkalemic periodic paralysis?

A

low K+ die, avoid fasting & strenuous exercise

ingestion of carbohydrates and slight exercise at onset of weakness may prevent the attack

thiazide diuretics or acetazolamide for prevention

94
Q

What is the cause of autosomal dominant myotonia congenita (Thomsen’s Disease)? Most commonly affected demographics?

A

Chloride channel mutation

M=F (more severe in M); infants

95
Q

Typical age of onset for autosomal dominant myotonia congenita (Thomsen’s Disease)? Symptoms?

A
  • infants - myotonia at birth
    • peculiar cry
    • difficulty feeding
    • inability to re-open eyes while having face washed
  • myotonia worse in the cold
    • athletic ability poor b/c slow & stiff movement
    • unable to play winter sport
    • complete long-distance events
96
Q

Diagnosis & treatment of Autosomal dominant myotonia congenita (Thomsen’s Disease)?

A
  • diagnosis: EMG
  • Treatment: mexiletine, phenytoin, procainamide

Neuro II (30 decks)

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