My Op a Thy

8/2/2019 My Op a Thy

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Myopathies

Joseph Lubeck, DO


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Myopathies- General Principles

Progressive proximal weakness, usually

painless

Normal sensory function

Normal or reduced DTRs

Proximal atrophy

CPK

markedly increased in necrotic, inflammatorymyopathies

mild-moderately increased in atrophic myopathies


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MyopathiesLab Findings

Type Atrophic Necrotic Degenerative Infiltrative

CPK NmlMod or

marked incrNml or mild incr Nml

EMGNml or

myopathic

Myopathic

Irritable

Myopathic

Irritable

Normal or

myopathic

Biopsy

Fiber

atrophy

Necrosis

Inflammation

Vascular

degeneration

Interstitial

inflammation


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Polymyositis - Dermatomyositis

Clinical features

more common in females

peak incidence 5-15, 45-55

Usually presents subacutely (wks - months)Initial Eventual

hip weakness 42% 98%

shoulder weakness 8% 78%

dysphagia 2% 54%

muscle pain 15% 58%

rash 8%


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Classification of Polymyositis

I. Polymyositis

II. Dermatomyositis

III. Polymyositis and Collagen Vascular Disease

IV. Dermatomyositis associated with malignancyV. Childhood dermatomyositis

Dermatomyositis Polymyositis

More homogeneous Heterogeneous

High incidence of ca Only 4% with caLittle association with CVD Associated with CVD

Greater severity May be mild


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Laboratory

elevated CPK - often > 10X ULN

Muscle Biopsy

Perivascular infiltrationInterstitial fibrosis

Dermatomyositis - perifasicular atrophy

Treatment

Corticosteroids


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Inclusion Body Myositis

Clinical Features

Age of onset > 30

Duration > 6 months

Weakness of proximal and distal arm and legmuscles

Finger/wrist flexor > finger/wrist extensors

Quadriceps


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Inclusion Body Myositis

Laboratory CPK < 12X normal

Biopsy

Inflammatory changes

Vacuolated muscle fibres EMG

Inflammatory changes

Treatment

Generally resistant to all therapies Reasonable to try steroids, immunosuppressants, IV

IgG


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Steroid Myopathy

Myopathic features of Cushings syndrome

and chronic corticosteroid therapy almost

identical

Is distinct difference between commonlyoccurring reduction in muscle bulk and

myopathic weakness

May be more common with longer acting

(fluorinated) corticosteroids

Rarely begins before 3 months of steroid

thera and ro ress until dosa e reduced


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Clinical features

Weakness beginning in pelvifemoral muscles.

May progress to trunk, neck and arms

LaboratoryCPK - normal

EMG - often normal

Treatment

Switch to shorting acting preparation and/or

alternate day therapy


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Acute Hypokalemic Myopathy

Course

K+ < 3.5 --- weakness, fatigue, myalgia

K+ < 2.5 --- moderate proximal weakness, CPK

may increase

K+ < 2.0 --- proximal limb weakness, muscle

pain

Prognosis

Improves within days after K+ replacement


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Duchennes Muscular Dystrophy

Clinical Manifestations

Often presents with delayed motor milestones,

clumsiness ------> progressive weakness

Weakness begins in pelvifemoral muscles ---->

shoulder girdle ----> distal and intercostal mm. Wheelchair bound by age 7-10, death by 20

Pseudohypertrophy of calves

Mild mental retardation and cardiac involvement

Gowers sign


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Gowers Sign


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Duchennes Muscular Dystrophy

Etiology

Sex linked recessive

Gene located at short arm of X chromosome

codes for dystrophin (>2000 kilobases)

Dystrophin absent in skeletal muscle of DMD

patients

Dystrophin also in cardiac and smooth muscle

?genetic engineering


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Lab

CPK massively elevated, often 1000 X nml

As muscle mass decreases, CPK falls

CPK never normal at birth or preclinical stagesBiopsy

interstitial inflammation, adipose tissue,

fibrosis

Treatment

genetic counseling - identify female carriers

maintain ambulation as late as ossible


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Tongue Myotonia


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Myotonic Disorders

Myotonia - repetitive discharge of muscleusually after voluntary contraction which

results in delayed or difficult relaxation

EMG with divebomber discharge


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Myotonic Dystrophy

Genetics - autosomal dominant

Age of onset - usually age 20-25. May be

congenital or present in middle age

Weaknessprimarily distal - hands and distal lower extr.

bulbar - dysarthria, dysphagia, ptosis

hatchet facies - due to temporalis atrophy


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Myotonic Facies


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Myotonic Dystrophy

Systemic involvementsmooth muscle - pharynx, esophagus, uterus

cardiac - conduction defects, arrhythmias

brain - decreased IQendocrine - testicular atrophy, diabetes

eye - cataracts

skin - frontal balding

Pathology

increased internal nuclei, ring fibers


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Myotonia Congenita

Geneticsautosomal dominant or recessive

Clinical

marked muscular hypertrophyno weakness or systemic involvement


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Facioscapulohumeral Dystrophy

Genetics - autosomal dominant

Clinical manifestations

variable

onset usually age 5-20facial weakness, difficulty with eye closure

scapular winging

Popeye arm - weakness/atrophy of biceps

and triceps with deltoid spared

anterior tibial weakness

CPK usually 2-3 X normal


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Muscular Dystrophies

Type GeneticsAge of

OnsetProgression Muscles Other

DuchenneX linked

recessive2-10 Rapid

Hips, shoulders,

quads, calves,

trunk

Heart, CNS

Myotonic AD 2-50 SlowFace, bulbar,

hands

Heart, GI, GU,

skin, eyes, endo

CNS

FSH AD 10-40 SlowFace, shoulders,

biceps, triceps None

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