Myopathies Flashcards

1
Q

What is the Ddx for weakness?

A
  1. Metabolic disturbances due to endocrine/electrolyte abnormalities
  2. Systemic illness from infection, immunologic or neoplastic origin
  3. UMN disease
  4. Neuromuscular disease
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2
Q

What is a myopathy?

A

A disease of muscles resulting in weakness and variable pain and wasting

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3
Q

What are the three types of myopathies?

A
  1. Muscular dystrophy
  2. Inflammatory myopathies
  3. Metabolic myopathies
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4
Q

What features are associated with dystrophic myopathies?

A
  1. Fiber splitting

2. Increased connective tissue

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5
Q

What are the different types of muscular dystrophy?

A
  1. Duchenne
  2. Becker
  3. Fascio-scapulo-humeral (FSH)
  4. Myotonic
  5. Limb girdle
  6. Emery-Dreifuss
  7. Oculo-pharyngeal
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6
Q

What are the main areas of weakness in Duchenne MD?

A

Proximal upper and lower limbs

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7
Q

What are the main areas of weakness in Emery-Dreifuss MD?

A

Proximal upper limb and distal lower limb

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8
Q

What are the main areas of weakness in Limb Girdle MD?

A

Proximal upper and lower limbs

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9
Q

What are the main areas of weakness in Fascio-scapulo-humeral (FSH) MD?

A

Proximal upper limbs + calfs + face

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10
Q

What are the main areas of weakness in Oculopharyngeal MD?

A

Proximal upper and lower limbs + eyes + throat

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11
Q

Describe the genetics and onset of Duchenne’s MD

A

X-Linked recessive
Xp21 large deletion
Onset at age 5

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12
Q

Describe the genetics and onset of Becker MD

A

X-Linked recessive
Xp21
Onset at age 10

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13
Q

Describe the genetics and onset of FSH MD

A

Autosomal Dominant
Chromosome 4
Onset 10-20

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14
Q

Describe the genetics and onset of Myotonic MD

A

Autosomal Dominant
Chromosome 19
Onset 15-30

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15
Q

Describe the genetics and onset of Limb Girdle MD

A

AR/AD

Onset 10-30

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16
Q

What is the initial weakness in Duchenne’s MD?

A

Pelvic- will have Gower’s Sign

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17
Q

What is the initial weakness in Becker’s MD?

A

Pelvic

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18
Q

What is the initial weakness in FSH MD?

A

Shoulder

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19
Q

What is the initial weakness in Myotonic MD?

A

Distal Weakness

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20
Q

What is the initial weakness in Limb Girdle MD?

A

Pelvic-Shoulder

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21
Q

Which muscular dystrophies show early facial weakness?

A

FSH and Myotonic MD

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22
Q

Which muscular dystrophies show late facial weakness?

A

Duchenne and Becker MD

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23
Q

Which MD spares the face?

A

Limb Girdle MD

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24
Q

Which muscular dystrophy has a rapid progression?

A

Duchenne’s MD

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25
Q

Which muscular dystrophies have elevated CK?

A

Duchenne + Becker + Limb Girdle

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26
Q

Which MD has a normal EKG?

A

FSH

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27
Q

Describe the muscle histology for Duchenne MD

A

Macrophage invasion + necrotic fibers

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28
Q

Patholophysiological difference between Duchenne and Beckers MD

A
Duchenne = Out of Frame mutation in Dystrophin
Beckers = In frame mutation in Dystrophin
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29
Q

What is the consequence of mutated Dystrophin?

A

It weakens the sarcolemma and leads to muscle necrosis

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30
Q

What are the clinical features of Duchenne’s MD?

A
  1. Difficulty running, waddling gait
  2. Calf Pseudohypertrophy
  3. Neck flexor weakness
  4. Lumbar Lordosis
  5. CI
  6. Wheel chair by 13
  7. Intestinal pseudo-obstruction
  8. Cardiomyopathy –> HF
  9. Respiratory failure
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31
Q

Typical age of death in patient with DMD?

A

20

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32
Q

What is the treatment for Duchenne’s MD?

A
  1. Prednisone

2. Deflazacort (best started by age 4-7)

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33
Q

How do steroids benefit patients with DMD?

A
  1. Prolong ambulation
  2. Delay respiratory failure
  3. Stabilize the sarcolemma
  4. Increase muscle mass
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34
Q

Why are 8% of female carriers of DMD symptomatic?

A

X-linked inactivation turns off the healthy dystrophin gene

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35
Q

What is the typical presentation in symptomatic female carriers of DMD?

A
  1. Mild risk of heart disease, muscle weakness and CI
  2. Myalgia
  3. Elevated CK and aldolase
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36
Q

Compare the symptoms of Becker’s MD to DMD

A

Beckers presents with calf pseudohypertrophy and early thigh weakness, but patients are less likely to have the GI obstruction, heart failure, CI and contractures seen in DMD patients

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37
Q

What will EMG show for DMD and Becker’s MD?

A

Myopathic Units

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38
Q

What are non-medical treatments appropriate for Becker’s MD?

A
  1. Genetic Counseling
  2. Physical Therapy
  3. Orthopedic Complication
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39
Q

What is the genetic association with fascioscapulohumeral MD?

A

Autosomal Dominant deletion of D4Z4 on 4q35

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40
Q

Describe the symptoms of FSH MD

A

Slow wasting of facial, scapular, humeral and perineal muscles, down sloping shoulders + winged scapular and prominent clavicles

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41
Q

Is life expectancy altered in FSH MD?

A

No

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42
Q

Which muscle groups are affected by Myotonic Dystrophy 1?

A

Distal Muscle Groups

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43
Q

Which muscle groups are affected by Myotonic Dystrophy 2?

A

Proximal Muscle Groups

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44
Q

Which type of Myotonic Dystrophy is more common?

A

Type 1

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45
Q

What is the genetic association with the different types of Myotonic Dystrophy?

A

Type 1: CTG repeats in DMPK gene

Type 2: CCTG repeats in zinc finger protein 9

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46
Q

Which hereditary pattern is seen with Myotonic Dystrophy Type 1?

A

Anticipation

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47
Q

What are symptoms of Myotonic Dystrophy Type 1?

A
  1. Myotonia
  2. Cataracts
  3. Avoidant Personality
  4. Hypersomnia
  5. Hypogonadism
  6. Mental Retardation
  7. Cardiac issues
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48
Q

What is the genetic pattern observed in Limb Girdle Muscular Dystrophy Types 1 and 2?

A

Type 1: AD

Type 2: AR

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49
Q

Other than proximal muscles, which organ systems may be involved in LGMD?

A

Cardiac and Respiratory Systems

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50
Q

What is the genetic defect seen in EMMD Type 1?

A

Emerin Defect, AR mutation of Xq28

51
Q

What is the genetic defect seen in EMMD Type 2?

A

Lamin A/C, AD or AR

52
Q

Which sub-class of Emery Dreifuss MD is associated with contractures?

A

Type 1

53
Q

Which MD is associated with cardiac conduction abnormalities?

A

Type 1 Emery Dreifuss MD

54
Q

What is the inheritance pattern for Oculo-pharyngeal MD?

A

Autosomal Dominant

55
Q

When is the typical onset of OPMD?

A

Middle age

56
Q

What is the pathological cause of OPMD?

A

Defect in the polyadenylate-binding protein (PABN1 due to GCG expansion or PABN2 due to GCA expansion)

57
Q

What chromosome is PABN on?

A

14

58
Q

What are the symptoms of OPMD?

A
  1. Ptosis
  2. Mild EOM weakness
  3. Dysphagia
  4. Mild limb weakness
  5. Reduced gag reflex
59
Q

What is the treatment for OPMD?

A

Oculoplasty or PEG

60
Q

What is the age of onset for Polymyositis?

A

45-65

61
Q

Which gender is more commonly affected by Polymyositis?

A

Women

62
Q

What is the clinical presentation of Polymyositis?

A

Weak onset proximal muscle weakness + falls + lung and cardio involvement

63
Q

How are dermatomyositis and polymyositis diagnosed?

A

CK + EMG and Bx

64
Q

What is the treatment for Dermatomyositis and Polymyositis?

A

Immunosuppression

65
Q

What is seen on histology with Polymyositis?

A

Endomysial inflammation

66
Q

What is the age presentation for Dermatomyositis?

A

Bimodal (5-14 and 45-65)

67
Q

Which gender is more commonly affected with Dermatomyositis?

A

Women

68
Q

What is the clinical presentation of Dermatomyositis?

A

Rapid onset proximal weakness + heliotrope rash + Gottron’s Sign + lung and cardio involvement

69
Q

What disease may be associated with breast and lung malignancy?

A

Dermatomyositis (25%)

70
Q

What disease is associated with Gottron’s Papules on the hands?

A

Dermatomyositis

71
Q

What is seen on histology with Dermatomyositis?

A

Perifascicular Atrophy

72
Q

What is the most common inflammatory myopathy in adults over 50?

A

Inclusion Body Myositis

73
Q

Which gender is more commonly affected by inclusion body myositis?

A

Men

74
Q

What is the clinical presentation of inclusion body myositis?

A

Slow onset proximal and distal weakness + dysphagia

75
Q

Which muscles are involved in inclusion body myositis?

A

Fingers and wrist flexors + quads + hip flexors

76
Q

How is inclusion body myositis diagnosed?

A

CK + EMG + Bx

77
Q

What is seen on biopsy of inclusion body myositis?

A

Rimmed vacuoles with amyloid inclusions + endomysial inflammation

78
Q

How does inclusion body myositis respond to immunosuppression?

A

Poorly

79
Q

Which myopathies are associated with cancer?

A

Dermatomyositis and Polymyositis

80
Q

Which myopathy involves distal and proximal muscles and is often asymmetric?

A

Inclusion body myositis

81
Q

What is the EMG result for Inclusion Body Myositis?

A

Myopathic + Neuropathic

82
Q

Which inflammatory myopathy has the best response to steroids?

A

Dermatomyositis

83
Q

What are the general causes of metabolic myopathies?

A
  1. Glycogen metabolism
  2. Lipid metabolism
  3. Electrolyte imbalance
  4. Mitochondria
84
Q

What are the symptoms of disorders of glycogen and lipid metabolism?

A
  1. Exercise intolerance

2. Myoglobinuria and elevated CK following exercise

85
Q

What are the genetics of most glycogen and lipid metabolic disorders?

A

Autosomal Recessive enzyme deficiencies

86
Q

EMG findings for glycogen and lipid metabolic disorders are

A

Myopathic

87
Q

How is the diagnosis of glycogen or lipid metabolic disorders made?

A

Biochemical analysis of muscle Bx

88
Q

What is the deficiency in Pompe Disease?

A

Type II Acid Maltase

89
Q

What are the symptoms of Pompe Disease?

A

Proximal muscle weakness + early respiratory insufficiency

90
Q

What is the deficiency in Cori-Forbes Disease?

A

Type II Debrancher Deficiency

91
Q

What are the symptoms of Cori-Forbes Disease?

A

Distal weakness + cardiomyopathy + PN

92
Q

What is the deficiency in McArdle’s Disease?

A

Type V Myophosphorylase Deficiency

93
Q

What are the symptoms of McArdle’s Disease?

A

Camps + Myoglobinuria + Second Wind Phenomenon

94
Q

What is the deficiency seen in Tarui Disease?

A

Type VII Phosphofructokinase Deficiency

95
Q

What are the symptoms of Tarui Disease?

A

Exercise intolerance + myoglobinuria

96
Q

Explain the consequences of a Carnitine Palmitoyl Transferase II Deficiency

A

Carnitine is required for the transport of FA into the mitochondria; symptoms flare up during fasting

97
Q

What are the symptoms of CPTII Deficiency?

A

Progressive proximal muscle weakness + tenderness and swelling of muscles with exercise + increased CK + myoglobinuria

98
Q

What is seen on Bx of CPTII Deficiency?

A

Lipid Storage Vacuoles

99
Q

Describe the clinical presentation of Hypokalemic Periodic Paralysis

A

Pt wakes up w/ weakness that lasts hours-days after having a large carb load of after exercise

100
Q

What is the underlying cause of hypokalemic periodic paralysis?

A

L-Type Ca Channelopathy

101
Q

Describe the clinical presentation of hyperkalemic periodic paralysis

A

Paralysis caused by a period of rest after fasting or exercise

102
Q

What is the underlying cause of hyperkalemic periodic paralysis?

A

SCN4A Na Channelopathy

103
Q

What is the Tx for Hyperkalemic Periodic Paralysis?

A

Eating or exercise

104
Q

Myotonia congenita is caused by

A

CLCM1 (Cl) Channelopathy

105
Q

Paramyotonia Congenia is caused by

A

CLCN1 or SCN4A Chennels

106
Q

Inheritance pattern for mitochondrial myopathies

A

Maternal

107
Q

Which type of myopathy is associated with neurologic symptoms?

A

Mitochondrial Myopathies

108
Q

How is the diagnosis of mitochondrial myopathies made?

A

By finding ragged reg fibers on muscle biopsy and biochemical analysis of muscle for specific oxidative enzymes

109
Q

What are the symptoms of Kearns-Sayre Syndrome?

A
  1. CPEO
  2. Retinitis Pigmentosa
  3. Heart Block
110
Q

What are the causes of provoked necrotizing polymyopathy?

A

Crush Injury, EtOH or extreme exertion

111
Q

Which patients are more susceptible to provoked necrotizing polymyopathy?

A

Pts with Glycogen disorders

112
Q

What is the clinical presentation of provoked necrotizing polymyopathy?

A

Pigmenturia + Tender Muscles

113
Q

What is the Tx for provoked necrotizing polymyopathy?

A

IV Fluids + monitor CK + rarely dialysis

114
Q

Which patients are more susceptible to malignant hyperthermia?

A

Pts with defects of Phosphodiesterase or RYR1 mutation

115
Q

What is the clinical presentation of malignant hyperthermia?

A

Fasciculations + increased tone + temperature increase + rigidity following anesthetics (Halothane and Succinylcholine)

116
Q

Tx for malignant hyperthermia?

A

Dantrolene + cooling blankets

117
Q

What are the symptoms seen with Hypothyroid Myopathy?

A
  1. Muscle cramps and proximal weakness
  2. Delayed reflexes
  3. Myoedema
  4. Myokymia
  5. Elevated CK
118
Q

Which patients are more likely to develop critical illness myopathy?

A

ICU patients on high dose steroids or paralytics + ventilator patients

119
Q

Describe the myopathy seen with acromegaly

A

Mild proximal muscle weakness

120
Q

Describe the myopathy seen with Cushing’s

A

Proximal weakness of the lower extremities

121
Q

Describe the EMG findings for a myopathy

A

Low amplitude + short duration + polyphasic with rapid recruitment

122
Q

Steroids result in what type of myopathy

A

Proximal Muscle Myopathy

123
Q

Common medication that causes myopathy

A

Statins

124
Q

Medication causing mitochondrial myopathy

A

AZT