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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
Emery-Dreifuss muscular dystrophy characteristic triad
- Early contractures of the elbow, ankle, and posterior neck - Progressive weakness and wasting - Cardiomyopathy
26
Progressive weakness and wasting in Emery-Dreifuss MD
- Proximal upper extremity - Distal lower extremity - Scapulohumeroperoneal muscle wasting
27
Cardiomyopathy in Emery-Dreifuss MD
- Cardiac conduction defect | - May not coexist with detectable muscle weakness
28
Types of Emery-Dreifuss MD
- X-linked | - Autosomal dominant form
29
Emery-Dreifuss X-linked form
- STA gene on Xq28 - Codes for nuclear membrane protein – emerin - Complete absence of emerin in most patients
30
Emery-Dreifuss autosomal dominant form
- LMNA gene at 1q21 - Codes for inner nuclear membrane proteins - lamin A and lamin C
31
Lamins
- 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
32
Fascioscapulohumeral muscular dystrophy
- Autosomal dominant inheritance - Deletion on chromosome 4 - Slowly progressive - Intellectual function remains intact
33
Fascioscapulohumeral MD involves muscles of
- "Mask-like” facial appearance - Shoulder girdle - Proximal upper extremities
34
Fascioscapulohumeral MD onset
- 3rd to 4th decade | - Earlier onset = poorer prognosis
35
Fascioscapulohumeral MD diagnosis
- CK levels – normal to mildly elevated | - EMG and biopsy
36
Fascioscapulohumeral MD classic findings
- 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
37
Fascioscapulohumeral MD other findings
- Lower extremity - Drop foot – early on - Peroneals and anterior tibialis - Assisted ambulation - Exophthalmos - Mild labile hypertension
38
Fascioscapulohumeral MD treatment
- Palliative - Scapular stabilization - Ankle foot orthoses
39
Limb-Girdle dystrophy
- Autosomal transmission - Genetic defect: abnormal dystrophin-glycoprotein complex - Sarcolemmal instability and muscle cell necrosis occur
40
Limb-Girdle dystrophy muscles affected
- Shoulder and pelvic girdle - Proximal muscular weakness - Facial involvement minimal
41
LGMD-1
- Autosomal dominant transmission - Second to third decade - Currently five identified types
42
LGMD-2
- Autosomal recessive - Late first to second decade - Currently nine identified types - Slow course over 20 to 30 years
43
LGMD onset and course
- LGMD-1 - LGMD-2 - Cardiomyopathy - Pulmonary insufficiency
44
LGMD treatment
- Physical therapy | - Cardiac and pulmonary care
45
Myotonic dystrophy
- Most common adult form of myopathy - Autosomal dominant disorder - Three recognized forms
46
Myotonic dystrophy DM1 (Steinerts disease)
- Chromosome 19 | - Common adult form
47
Myotonic dystrophy DM2 (proximal myotonic myopathy)
- Chromosome 3 | - Juvenile form
48
Congenital myotonic dystrophy
- Chromosome 19 | - Infantile variety
49
Myotonic dystrophy presentation
- 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
Myotonic dystrophy incidence and onset
- 1/8000 – 10,000 | - Life span - ~ 6 decades
51
Myotonic dystrophy clinical findings
- Intellectual impairment – 80% of patients - Subcapsular cataracts - Muscular weakness: - Distal extremity muscles - Facial and neck → muscles hatchet face - Premature frontal balding
52
Myotonic dystrophy diagnosis
- Presence of cataracts - Cardiac conduction defect - First degree heart block - Weak respiratory muscles - ↑ Creatine kinase - Muscle biopsy - Fiber I atrophy
53
Myotonic dystrophy treatment
- Aimed at managing symptoms and minimizing disability | - Rehabilitation medicine
54
Myotonic dystrophy medications
- 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
Myotonia Congenita
- Autosomal dominant: Thomsen Disease - Autosomal recessive: Becker Disease - Slight weakness - No cardiac involvement
56
Myotonia congenita treatment
- Anti-myotonic drugs - Phenytoin - Quinine - Procainamide - Acetazolamide - Tocainide
57
Distal muscular dystrophy variants
- Early onset | - Late onset
58
Early onset distal muscular dystrophy
- Sporadic with distal leg weakness - Occurs in 2nd to 3rd decade - Marked ↑ CK
59
Late onset distal muscular dystrophy
- Autosomal dominant - Begins in legs – AT and calf muscles - Cardiomyopathy - Welander form – affects the small muscles of hands
60
Role of thyroid gland
- Absorbs dietary iodine - Synthesizes T3 (thyrotropin): 20% of normal thyroid hormone - Synthesized T4 (thyroxine): 80% of normal thyroid hormone
61
Pituitary gland
- Controls the thyroid - Produces TSH which is regulated by T3 and T4 levels - End result: control of cellular metabolism
62
Thyroid regulated metabolism
- Thyroid gland – T3 and T4 – regulate metabolism - Pituitary gland – TSH – regulate T3 and T4 synthesis - Hypothalamus – TRH – regulates pituitary
63
Hyperthyroidism effects on muscles
- Occasional muscle weakness
64
Hypothyroidism effects on muscle
- Muscle pain and weakness - Creatine kinase may be elevated - May have muscular hypertrophy - Delayed recovery of deep tendon reflex responses
65
Hyperparathyroidism effects on muscles
- May be associated with muscle weakness - “Pain” is secondary to underlying bone disease - Possible muscular hypertrophy - Hyperreflexia
66
Hypoparathyroidism effects on muscles
- Neurological signs consistent with tetany - Must rule out polymyositis due to high CK - Hyporeflexia
67
Adrenal disorders
- Endogenous elevations may produce myopathy
68
Pituitary disorders
- Acromegaly – secondary muscle enlargement | - Pan-hypopituitaryism associated with thyroid and parathyroid disorders
69
Vitamin deficiencies
- Mal-absorption disorders | - Vitamin E and D muscular myopathies
70
Autoimmune mediated myopathies
- Non-suppurative (no exudate) inflammatory process - Weakness of shoulder and pelvic girdle - Polymyositis, dermatomyositis - May be associated with viral infection
71
Polymyositis
- Necrosis from activated T cells and macrophages
72
Dermatomyositis
- Necrosis from B lymphocytes and T4 cells
73
Inflammatory myopathies classification
- 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
Inflammatory myopathy diagnostic criteria
- 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
Primary idiopathic polymyositis incidence
- ~1/3 of all myopathies - Female to males – 2:1 - Distal muscles spared in 75% of cases - This is a proximal myopathy
76
Primary idiopathic polymyositis clinical presentation
- Proximal limb weakness - Shoulder girdle involvement - Pain in buttocks and thighs (achy, tender with deep palpation) - “Inflammatory” symptoms
77
Primary idiopathic polymyositis histopathology
- 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
Primary idiopathic polymyositis characteristic skin changes
- Skin changes may precede muscle weakness | - Amyopathic dermatomyositis –skin findings only
79
Primary idiopathic polymyositis autoantibodies
- Jo-1 – pulmonary involvement | - Mi-2 – 25% of all patients (specific but not sensitive)
80
Primary idiopathic dermatomyositis skin findings
- Gottron's papules - Heliotrope rash - Violaceous to dusky color - Periungual erythema - Photosensitive poikiloderma (Shawl sign) - Hyperkeratosis of palms and fingers
81
Gottron's papules (dermatomyositis)
- Diffuse erythema over bony prominences - Often telangiectatic - Often pruritic
82
Violaceous to dusky color (dermatomyositis)
- Symmetrical distribution | - Involves periorbital area
83
Periungual erythema (dermatomyositis)
- Nail-fold capillary changes - Raynaud’s phenomenon - Hypertrophy of the cuticle
84
Hyperkeratosis of palms and fingers (dermatomyositis)
- Darkened horizontal lines on lateral and palmar aspect of fingers
85
Primary idiopathic dermatomyositis systemic changes
- 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
Polymyositis or dermatomyositis associated with neoplasm
- 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
Childhood polymyositis or dermatomyositis with vasculitis
- Dermatomyositis more common - 8 to 20% of immune myopathies - Etiology unknown
88
Childhood polymyositis or dermatomyositis with vasculitis clinical presentation
- 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
Childhood Polymyositis or Dermatomyositis with Vasculitis diagnosis
- MRI - Muscle biopsy - Blood tests - Nailfold capillaroscopy
90
Nailfold capillaroscopy
- 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
Childhood polymyositis or dermatomyositis with vasculitis treatment
- 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
Polymyositis or dermatomyositis with associated connective tissue disease
- 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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