SKELETAL MUSCLE PATHOLOGY

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SKELETAL MUSCLE PATHOLOGY
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Normal skeletal muscle
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Pathophysiological changes of muscles

• Atrophy and hypertrophy of muscles

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Atrophy and hypertrophy of muscles
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Muscle atrophies

• Muscle atrophy is defined as a decrease in the
  mass of the muscle
• Physiologically Muscle mass, muscle strength,
  and bone density decrease in the elderly
• Disuse atrophy of muscles can occur after
  prolonged immobility such as extended bed-rest,
  or having a body part in a cast.
• This type of atrophy can usually be reversed with
  exercise.

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Disuse Atrophy Of Muscles
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• There are many diseases and conditions which
  cause atrophy of muscle mass.
• For example diseases such as cancer and AIDS
  induce a body wasting syndrome called "cachexia
• Other conditions which can induce skeletal muscle
  atrophy are congestive heart failure and liver
  disease.

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Severe generalized muscle atrophy Body wasting
syndrome called "Cachexia
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Muscle hypertrophy

• Muscle hypertrophy is an increase in the size of
  a muscle
• Hypertrophy is an increase in mass of a muscle
  that can be induced by a number of stimuli. The
  most familiar of these is exercise.
• Pathologically in Acromegaly disease there is
  pathological muscle hypertrophy affecting mainly
  the type (1) skeletal fibers

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Exercise Muscle Hypertrophy
Acromegaly Disease
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Muscle Diseases
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Classification of Muscle Disease

• Inflammatory Myopathies
• Infectious Myositis
• Non-Infectious Myositis (Auto-immune )
• 1-Polymyositis
• 2-Dermatomyositis
• 3-Inclusion body myositis
• Diseases of the Neuromuscular Junction
• -Myasthenia Gravis
• -Lambert-Eaton Syndrome

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• Dystrophies
• Duchennes Muscular Dystrophy
• Beckers Muscular Dystrophy
• Myotonic Dystrophy
• Metabolic Myopathies
• -Glycogen Storage Diseases
• -Mitochondrial Myopathies
• Toxic Myopathies

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Inflammatory Myopathies
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Inflammatory myositis

• Polymyositis
• Dermatomyositis
• Inclusion body myositis
• Are of auto-immune origin

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Polymyositis (PM)

• It means "inflammation of many muscles") it is a
  type of chronic inflammation of the muscles
  possibly due to autoimmune causes

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• Clinical presentation
• Adults
• Bilateral proximal muscle weakness
• Microscopic
• Endomysial lymphocytic inflammation
• Skeletal muscle fiber degeneration and
  regeneration

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POLYMYOSITIS mostly affects the muscles of the
hips and thighs, the upper arms, the top part of
the back, the shoulder area and the neck
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Signs and symptoms

• Symptoms include pain with marked weakness and
  loss of muscle mass in the proximal musculature
  particularly in the shoulder and pelvic girdle.
• The hip extensors are often severely affected
  leading to particular difficulty in ascending
  stairs and rising from a seated position.
• Dysphagia (difficulty in swallowing) occurs in
  1/3 of patients.
• Low grade fever and peripheral lymphadenopathy
  may be present.

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Muscle weakness can cause difficulty in many
daily activities
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Diagnosis

• History and physical examination
• Elevation of creatine kinase
• Electromyograph (EMG) alteration
• Positive muscle biopsy

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Endomysial lymphocytic inflammation
Polymyositis
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Dermatomyositis

• Dermatomyositis (DM) is a connective-tissue
  disease related to polymyositis (PM) that is
  characterized by inflammation of the muscles and
  the skin.
• The disease may also affect the joints, the
  esophagus, the lungs, and, less commonly, the
  heart.

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Dermatomyositis

• Clinical presentation
• Children and adults
• Bilateral proximal muscle weakness
• Skin rashes (upper eyelids)
• Peri-orbital edema
• Microscopic
• Perimysial and vascular lymphocytic inflammation
• Skeletal muscle fiber degeneration and
  regeneration

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• Grotton lesions scaly erythematous eruptions or
  red patches overlying the knuckles, elbows, and
  knees
• X-ray findings sometimes include dystrophic
  calcifications in the muscles, and patients may
  or may not notice small calcium deposits under
  the skin

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Gottron's papules Discrete erythematous papules
overlying the metacarpal and interphalangeal
joints in a patient with juvenile dermatomyositis
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Gottron's sign. Confluent macular erythema with
scale confined to the skin overlying the patellae
in a juvenile dermatomyositis
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X-Ray of the knee in a patient with
dermatomyositis
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Clinical presentation

• The main symptoms include skin rash and symmetric
  muscle weakness which may be accompanied by pain.
• The heliotrope or "lilac" rash is a violaceous
  eruption on the upper eyelids and in rare cases
  on the lower eyelids as well, often with itching
  and swelling

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Eruption is associated with peri-orbital edema
and telangiectasias of the both eyelids.
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Diagnosis

• The diagnosis of dermatomyositis is usually
  confirmed by muscle biopsy, EMG and blood tests.
• Liver enzymes, specifically creatin phosphokinase
  (CPK), are the major tool in assessing the
  progress of the disease and/or the efficacy of
  treatment

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Perimysial and vascular lymphocytic inflammation
Dermatomyositis
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Inclusion body myositis

• IBM causes progressive weakness of the muscles of
  the wrists and fingers, the muscles of the front
  of the thigh and the muscles that lift the front
  of the foot.
• IBM is generally a slowly progressive disease,
  and life expectancy isnt significantly affected.
  Most people with IBM remain able to walk,
  although they may require a cane or wheelchair
  for long distances.

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• Clinical presentation
• Adultsgt age 50
• Asymmetrical distal muscle weakness
• Microscopically
• Cytoplasmic vacuoles with basophilic granules and
  amyloid

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The first muscles affected in inclusion-body
myositis are usually those of the wrists and
fingers, and the muscles at the front of the
thigh. The muscles that lift the front of the
foot also may be affected
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Diagnosis

• Elevated creatine kinase CK levels
• Electromyography (EMG) studies usually display
  abnormalities.
• Muscle biopsy display several findings including
  inflammatory cells invading muscle cells,
  vacuolar degeneration, inclusions or plaques of
  abnormal proteins.

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Cytoplasmic vacuoles
Inclusion body myositis