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Pod Med III > 8) Muscular Dystrophies and Metabolically Mediated Muscular Weakness > Flashcards

8) Muscular Dystrophies and Metabolically Mediated Muscular Weakness Flashcards

1
Q

Myopathies

A
  • Characterized by PROXIMAL muscle weakness
  • Neuropathies usually are DISTAL
  • Actual preservation of or apparent increase in muscle bulk
  • Preservation of deep tendon reflexes
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2
Q

Myopathy etiologies

A
  • Hereditary
  • Metabolic
  • Inflammatory
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3
Q

Muscular dystrophies presenting in childhood

A
  • Duchenne
  • Becker
  • Emery-Dreifuss
  • Fascioscapulohumeral
  • Limb-girdle
  • Congenital
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4
Q

Inflammatory myopathies presenting in childhood

A
  • Dermatomyositis

- Polymyositis (rarely)

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5
Q

Congenital myopathies presenting in childhood

A
  • Nemaline
  • Centronuclear
  • Central core
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6
Q

Normal motor milestones

A
  • 4 mo. – reaches for toys
  • 5 mo. – rolls over
  • 6 mo. – sits alone
  • 8 mo. – crawls
  • 7-9 mo. – stands alone
  • 12 mo. – walks alone
  • 15 mo. – walks well
  • 18 mo. – runs
  • 3 yrs. – heel to toe gait
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7
Q

Muscle diseases laboratory evaluation

A
  • Elevation of CK – MM band (high concentrations within sarcoplasm)
  • Aldolase
  • Lactate dehydrogenase
  • AST
  • ALT
  • Acute phase reactants?
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8
Q

Acute phase reactants in muscle disease lab eval

A
  • ESR
  • C-reactive protein
  • Fibrinogen
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9
Q

Duchenne muscular dystrophy

A
  • Most commonly known
  • X-linked recessive disorder
  • Translocation and/or deletion on X chromosome
  • Affects normal production of dystrophin
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10
Q

Duchenne muscular dystrophy incidence

A
  • 13-33/100,000 live males

- 1/3 cases – new mutation

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11
Q

Dystrophin

A
  • Component in dystrophin-associated glycoprotein complex
  • Located between sarcolemma and myofibrils
  • Supports muscle fiber length
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12
Q

Absence of dystrophin leads to

A
  • Cytoskeleton disruption
  • Sarcolemmal instability
  • Abnormal calcium homeostasis
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13
Q

Duchenne muscular dystrophy clinical presentation

A
  • Delayed motor milestones
  • Symptoms evident at 3-5 yrs.
  • Proximal muscle weakness
  • Clumsy gait
  • Gower’s Sign
  • Calf pseudohypertrophy
  • Classic presentation
  • Calves are weak***
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14
Q

Duchenne muscular dystrophy symptoms age 7 to 8

A
  • Muscle contractions (achilles tendon, iliotibial band)
  • Loss of muscle strength
  • Proximal lower extremities
  • Neck flexors
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15
Q

Duchenne muscular dystrophy symptoms age 10

A
  • Assisted ambulation

- Use of wheelchair

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16
Q

Duchenne muscular dystrophy life expectancy

A
  • Most pass away in their 20s
  • Pulmonary infections
  • Congestive heart failure
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17
Q

Duchenne’s muscular dystrophy serology

A
  • ↑ CK levels – 20-100x normal
  • ↑ Troponin I
  • ↑ SGOT and SGPT
  • Genetic Testing
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18
Q

Duchenne’s muscular dystrophy muscle biopsy

A
  • Muscle fibers of varying size
  • Small groups of necrotic and regenerating fibers
  • Muscle fibers replaced with connective tissue and fat
  • Staining for dystrophin absent
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19
Q

Duchenne MD treatment

A
  • No known cure for DMD
  • Treatment aims to control symptoms to improve quality of life
  • Glucocorticoids can slow the loss of muscle strength: Prednisone and Deflazacort
  • Benefits outweigh side effects
  • Significant increase in strength, in muscle function and pulmonary function
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20
Q

Becker’s muscular dystrophy

A
  • X-linked dystrophinopathy

- Benign form of pseudohypertrophic muscular dystrophy

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21
Q

Becker’s muscular dystrophy incidence and onset

A
  • 1/10 of Duchenne’s
  • Dystrophin levels – 30-80% of normal
  • Rarely diagnosed before age 5
  • Walking continues beyond age 15
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22
Q

Beckers MD characterized by

A
  • Progressive proximal limb weakness
  • Scoliosis
  • Muscular contractures
  • Fatigue
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23
Q

Becker’s MD diagnosis

A
  • Muscle weakness
  • ↑ Creatine kinase -MM
  • EMG
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24
Q

Becker’s MD treatment (physical)

A
  • Exercise and PT (minimize abnormal, painful joint position
    Slow down development of scoliosis)
  • Rehabilitation devices (maintain mobility and independence)
  • Respiratory care
  • Surgery (reduce muscle contractures)
  • Gene therapy
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25
Q

Emery-Dreifuss muscular dystrophy characteristic triad

A
  • Early contractures of the elbow, ankle, and posterior neck
  • Progressive weakness and wasting
  • Cardiomyopathy
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26
Q

Progressive weakness and wasting in Emery-Dreifuss MD

A
  • Proximal upper extremity
  • Distal lower extremity
  • Scapulohumeroperoneal muscle wasting
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27
Q

Cardiomyopathy in Emery-Dreifuss MD

A
  • Cardiac conduction defect

- May not coexist with detectable muscle weakness

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28
Q

Types of Emery-Dreifuss MD

A
  • X-linked

- Autosomal dominant form

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29
Q

Emery-Dreifuss X-linked form

A
  • STA gene on Xq28
  • Codes for nuclear membrane protein – emerin
  • Complete absence of emerin in most patients
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30
Q

Emery-Dreifuss autosomal dominant form

A
  • LMNA gene at 1q21
  • Codes for inner nuclear membrane proteins
  • lamin A and lamin C
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31
Q

Lamins

A
  • Provide structural stability to the cell nucleus
  • Define its shape
  • Provide the scaffolding for the proteins required for nuclear functions
  • Emerin is an important nuclear membrane protein
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32
Q

Fascioscapulohumeral muscular dystrophy

A
  • Autosomal dominant inheritance
  • Deletion on chromosome 4
  • Slowly progressive
  • Intellectual function remains intact
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33
Q

Fascioscapulohumeral MD involves muscles of

A
  • “Mask-like” facial appearance
  • Shoulder girdle
  • Proximal upper extremities
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34
Q

Fascioscapulohumeral MD onset

A
  • 3rd to 4th decade

- Earlier onset = poorer prognosis

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35
Q

Fascioscapulohumeral MD diagnosis

A
  • CK levels – normal to mildly elevated

- EMG and biopsy

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36
Q

Fascioscapulohumeral MD classic findings

A
  • Facial weakness
  • Inability to whistle
  • Sullen expression
  • Shoulder girdle weakness
  • Scapular winging
  • Sloping shoulders
  • Serratus anterior,
    trapezium, and rhomboids
  • Upper extremity
  • Biceps and triceps late in disease process
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37
Q

Fascioscapulohumeral MD other findings

A
  • Lower extremity
  • Drop foot – early on
  • Peroneals and anterior tibialis
  • Assisted ambulation
  • Exophthalmos
  • Mild labile hypertension
38
Q

Fascioscapulohumeral MD treatment

A
  • Palliative
  • Scapular stabilization
  • Ankle foot orthoses
39
Q

Limb-Girdle dystrophy

A
  • Autosomal transmission
  • Genetic defect: abnormal dystrophin-glycoprotein complex
  • Sarcolemmal instability and muscle cell necrosis occur
40
Q

Limb-Girdle dystrophy muscles affected

A
  • Shoulder and pelvic girdle
  • Proximal muscular weakness
  • Facial involvement minimal
41
Q

LGMD-1

A
  • Autosomal dominant transmission
  • Second to third decade
  • Currently five identified types
42
Q

LGMD-2

A
  • Autosomal recessive
  • Late first to second decade
  • Currently nine identified types
  • Slow course over 20 to 30 years
43
Q

LGMD onset and course

A
  • LGMD-1
  • LGMD-2
  • Cardiomyopathy
  • Pulmonary insufficiency
44
Q

LGMD treatment

A
  • Physical therapy

- Cardiac and pulmonary care

45
Q

Myotonic dystrophy

A
  • Most common adult form of myopathy
  • Autosomal dominant disorder
  • Three recognized forms
46
Q

Myotonic dystrophy DM1 (Steinerts disease)

A
  • Chromosome 19

- Common adult form

47
Q

Myotonic dystrophy DM2 (proximal myotonic myopathy)

A
  • Chromosome 3

- Juvenile form

48
Q

Congenital myotonic dystrophy

A
  • Chromosome 19

- Infantile variety

49
Q

Myotonic dystrophy presentation

A
  • The failure of voluntary muscles to relax
  • Spasms and stiffening
  • Irregularities in the ion channels of muscle membranes
  • Steadily progressive disease
  • Distal weakness and myotonia (trouble relaxing a muscle)
50
Q

Myotonic dystrophy incidence and onset

A
  • 1/8000 – 10,000

- Life span - ~ 6 decades

51
Q

Myotonic dystrophy clinical findings

A
  • Intellectual impairment – 80% of patients
  • Subcapsular cataracts
  • Muscular weakness:
  • Distal extremity muscles
  • Facial and neck → muscles hatchet face
  • Premature frontal balding
52
Q

Myotonic dystrophy diagnosis

A
  • Presence of cataracts
  • Cardiac conduction defect
  • First degree heart block
  • Weak respiratory muscles
  • ↑ Creatine kinase
  • Muscle biopsy
  • Fiber I atrophy
53
Q

Myotonic dystrophy treatment

A
  • Aimed at managing symptoms and minimizing disability

- Rehabilitation medicine

54
Q

Myotonic dystrophy medications

A
  • Anti-diabetic drugs to normalize blood sugar levels
  • Anti-myotonic drugs (such as mexiletine) when myotonia impairs normal activities
  • Nonsteroidal anti-inflammatory drugs to manage muscle pain
55
Q

Myotonia Congenita

A
  • Autosomal dominant: Thomsen Disease
  • Autosomal recessive: Becker Disease
  • Slight weakness
  • No cardiac involvement
56
Q

Myotonia congenita treatment

A
  • Anti-myotonic drugs
  • Phenytoin
  • Quinine
  • Procainamide
  • Acetazolamide
  • Tocainide
57
Q

Distal muscular dystrophy variants

A
  • Early onset

- Late onset

58
Q

Early onset distal muscular dystrophy

A
  • Sporadic with distal leg weakness
  • Occurs in 2nd to 3rd decade
  • Marked ↑ CK
59
Q

Late onset distal muscular dystrophy

A
  • Autosomal dominant
  • Begins in legs – AT and calf muscles
  • Cardiomyopathy
  • Welander form – affects the small muscles of hands
60
Q

Role of thyroid gland

A
  • Absorbs dietary iodine
  • Synthesizes T3 (thyrotropin): 20% of normal thyroid hormone
  • Synthesized T4 (thyroxine): 80% of normal thyroid hormone
61
Q

Pituitary gland

A
  • Controls the thyroid
  • Produces TSH which is regulated by T3 and T4 levels
  • End result: control of cellular metabolism
62
Q

Thyroid regulated metabolism

A
  • Thyroid gland – T3 and T4 – regulate metabolism
  • Pituitary gland – TSH – regulate T3 and T4 synthesis
  • Hypothalamus – TRH – regulates pituitary
63
Q

Hyperthyroidism effects on muscles

A
  • Occasional muscle weakness
64
Q

Hypothyroidism effects on muscle

A
  • Muscle pain and weakness
  • Creatine kinase may be elevated
  • May have muscular hypertrophy
  • Delayed recovery of deep tendon reflex responses
65
Q

Hyperparathyroidism effects on muscles

A
  • May be associated with muscle weakness
  • “Pain” is secondary to underlying bone disease
  • Possible muscular hypertrophy
  • Hyperreflexia
66
Q

Hypoparathyroidism effects on muscles

A
  • Neurological signs consistent with tetany
  • Must rule out polymyositis due to high CK
  • Hyporeflexia
67
Q

Adrenal disorders

A
  • Endogenous elevations may produce myopathy
68
Q

Pituitary disorders

A
  • Acromegaly – secondary muscle enlargement

- Pan-hypopituitaryism associated with thyroid and parathyroid disorders

69
Q

Vitamin deficiencies

A
  • Mal-absorption disorders

- Vitamin E and D muscular myopathies

70
Q

Autoimmune mediated myopathies

A
  • Non-suppurative (no exudate) inflammatory process
  • Weakness of shoulder and pelvic girdle
  • Polymyositis, dermatomyositis
  • May be associated with viral infection
71
Q

Polymyositis

A
  • Necrosis from activated T cells and macrophages
72
Q

Dermatomyositis

A
  • Necrosis from B lymphocytes and T4 cells
73
Q

Inflammatory myopathies classification

A
  • Group I = primary idiopathic polymyositis
  • Group II = primary idiopathic dermatomyositis
  • Group III = dermatomyositis or polymyositis associated with neoplasm
  • Group IV = Childhood dermatomyositis or polymyositis associated with vasculitis
  • Group V = dermatomyositis or polymyositis associated with collagen vascular disease
74
Q

Inflammatory myopathy diagnostic criteria

A
  • Progressive and symmetrical proximal muscle weakness
  • Increased concentration of serum muscle enzymes
  • Abnormal EMG findings
  • Abnormal muscle biopsy(It’s the gold standard)
  • Cutaneous skin changes → dermatomyositis
75
Q

Primary idiopathic polymyositis incidence

A
  • ~1/3 of all myopathies
  • Female to males – 2:1
  • Distal muscles spared in 75% of cases
  • This is a proximal myopathy
76
Q

Primary idiopathic polymyositis clinical presentation

A
  • Proximal limb weakness
  • Shoulder girdle involvement
  • Pain in buttocks and thighs (achy, tender with deep palpation)
  • “Inflammatory” symptoms
77
Q

Primary idiopathic polymyositis histopathology

A
  • Muscle fibers in stages of necrosis and regeneration
  • Focal and endomysial inflammatory cell infiltrate
  • T-lymphocytes (T8+) with macrophage invade non-necrotic fibers
  • Destroyed fibers are replaced with fat and fibrous tissue
78
Q

Primary idiopathic polymyositis characteristic skin changes

A
  • Skin changes may precede muscle weakness

- Amyopathic dermatomyositis –skin findings only

79
Q

Primary idiopathic polymyositis autoantibodies

A
  • Jo-1 – pulmonary involvement

- Mi-2 – 25% of all patients (specific but not sensitive)

80
Q

Primary idiopathic dermatomyositis skin findings

A
  • Gottron’s papules
  • Heliotrope rash
  • Violaceous to dusky color
  • Periungual erythema
  • Photosensitive poikiloderma (Shawl sign)
  • Hyperkeratosis of palms and fingers
81
Q

Gottron’s papules (dermatomyositis)

A
  • Diffuse erythema over bony prominences
  • Often telangiectatic
  • Often pruritic
82
Q

Violaceous to dusky color (dermatomyositis)

A
  • Symmetrical distribution

- Involves periorbital area

83
Q

Periungual erythema (dermatomyositis)

A
  • Nail-fold capillary changes
  • Raynaud’s phenomenon
  • Hypertrophy of the cuticle
84
Q

Hyperkeratosis of palms and fingers (dermatomyositis)

A
  • Darkened horizontal lines on lateral and palmar aspect of fingers
85
Q

Primary idiopathic dermatomyositis systemic changes

A
  • Inflammatory myopathy (arthralgias, arthritis or both)
  • Pulmonary disease (proximal dysphagia of pharynx and esophagus, aspiration pathology)
  • Cardiac involvement (not common, carries more severe prognosis)
86
Q

Polymyositis or dermatomyositis associated with neoplasm

A
  • Myositis may be paraneoplastic syndrome
  • 20% of inflammatory myopathies
  • Skin and muscle changes are consistent with these myopathies
  • Malignancy is most typical of that for patients age group
  • CK levels are normally elevated (normal levels suggest increased possibility of malignancy)
87
Q

Childhood polymyositis or dermatomyositis with vasculitis

A
  • Dermatomyositis more common
  • 8 to 20% of immune myopathies
  • Etiology unknown
88
Q

Childhood polymyositis or dermatomyositis with vasculitis clinical presentation

A
  • Vasculitis in skin and muscles
  • Gastrointestinal involvement
  • Abnormal accumulations of calcium deposits (calcifications) in muscle and skin tissues
  • Necrotizing lesions of the skin
  • Ischemic infarction of kidneys, GI tract and brain are possible
89
Q

Childhood Polymyositis or Dermatomyositis with Vasculitis diagnosis

A
  • MRI
  • Muscle biopsy
  • Blood tests
  • Nailfold capillaroscopy
90
Q

Nailfold capillaroscopy

A
  • Causes abnormal swelling and distortion of the blood vessels around the nails
  • This finding suggests active disease
  • Examine the nailbeds by using a lighted magnifying tool
91
Q

Childhood polymyositis or dermatomyositis with vasculitis treatment

A
  • Goal is to minimize inflammation, improve function, and prevent disability
  • Corticosteroids
  • Corticosteroid-sparing agents
  • Cyclosporine, azathioprene, tacrolimus, hydroxychloroquine, mycophenalate mofetil, anti TNF drugs
  • Skin protection
  • PT
  • Speech therapy
  • Diet assessment
92
Q

Polymyositis or dermatomyositis with associated connective tissue disease

A
  • Overlap syndromes
  • Polymyositis has been associated with other connective-tissue diseases, including the following:
  • Systemic lupus erythematosus
  • Rheumatoid arthritis
  • Mixed connective-tissue disease
  • Sjögren syndrome
  • Scleroderma

Pod Med III (8 decks)

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