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Muscular Dystrophies

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Muscular Dystrophies Noor Anam Al Salihi Muscular Dystrophies A group of hereditary progressive diseases each with unique phenotypic and genetic features. – PowerPoint PPT presentation

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Title: Muscular Dystrophies


1
Muscular Dystrophies
  • Noor Anam Al Salihi

2
Muscular Dystrophies
  • A group of hereditary progressive diseases each
    with unique phenotypic and genetic features.
  • How to differentiate MYOPATHY from NEUROATHY?
  • Myopathy
    Neuropathy
  • -Weakness most marked proximally
    - Distally
  • -No muscle wasting or depression of
    - There is
  • tendon reflexes until at least advanced stage.
  • -Normal abdominal and plantar reflexes
    - Abnormal
  • -No sensory loss or sphincter disturbances.
    - May be present.

3
Duchenne
  • XR., sometimes called Pseudohypertrophic muscular
    dystrophy.
  • Incidence 30/100,000 live born males.
  • Clinical Features
  • Duchenne dystrophy is present at birth, but the
    disorder usually becomes apparent between ages 3
    and 5.
  • The boys fall frequently and have difficulty
    keeping up with friends when playing. Running,
    jumping, and hopping are invariably abnormal.
  • By age 5, muscle weakness is obvious by muscle
    testing.
  • On getting up from the floor, the patient uses
    his hands to climb up himself (Gowers' maneuver).

4
  • Gowers' sign showing a patient using arms to
    climb up the legs in attempting to get up from
    the floor.

5
  • Contractures of the heel cords and iliotibial
    bands become apparent by age 6, when toe walking
    is associated with a lordotic posture.

6
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7
  • Loss of muscle strength is progressive, with
    predilection for proximal limb muscles and the
    neck flexors leg involvement is more severe than
    arm involvement.
  • Between ages 8 and 10 walking may require the use
    of braces joint contractures and limitations of
    hip flexion, knee, elbow, and wrist extension are
    made worse by prolonged sitting. By age 12, most
    patients are wheelchair dependent.
  • Contractures become fixed, and a progressive
    scoliosis often develops that may be associated
    with pain. The chest deformity with scoliosis
    impairs pulmonary function, which is already
    diminished by muscle weakness. By age 16 to 18,
    patients are predisposed to serious, sometimes
    fatal pulmonary infections. Other causes of death
    include aspiration of food and acute gastric
    dilation.

8
  • Cardiac cause of death is uncommon despite the
    presence of a cardiomyopathy in almost all
    patients. Congestive heart failure seldom occurs
    except with severe stress such as pneumonia.
    Cardiac arrhythmias are rare.
  • Intellectual impairment in Duchenne dystrophy is
    common the average intelligence quotient (IQ) is
    1 SD below the mean. Impairment of intellectual
    function appears to be nonprogressive and affects
    verbal ability more than performance.

9
Lab. Features
  • Serum CK levels are invariably elevated to
    between 20 and 100 times normal. The levels are
    abnormal at birth but decline late in the disease
    because of inactivity and loss of muscle mass.
  • EMG demonstrates features typical of myopathy.
  • The muscle biopsy shows muscle fibers of varying
    size as well as small groups of necrotic and
    regenerating fibers. Connective tissue and fat
    replace lost muscle fibers.
  • A definitive diagnosis of Duchenne dystrophy can
    be established on the basis of dystrophin
    deficiency in a biopsy of muscle tissue or
    mutation analysis on peripheral blood leukocytes.

10
Treatment
  • Glucocorticoids, administered as prednisone in a
    dose of 0.75 mg/kg per day, significantly slow
    progression of Duchenne dystrophy for up to 3
    years.
  • Duchenne disease may benefit from novel therapies
    that either replace the defective gene or missing
    protein or implement downstream corrections
    (e.g., skipping mutated exons or reading through
    mutations that introduce stop codons).

11
Becker Muscular Dystrophy
  • This less severe form of X-linked recessive
    muscular dystrophy results from allelic defects
    of the same gene responsible for Duchenne
    dystrophy.
  • Becker muscular dystrophy is 10 times less
    frequent than Duchenne, with an incidence of
    about 3 per 100,000 live-born males.

12
Clinical Features
  • The pattern of muscle wasting in Becker muscular
    dystrophy closely resembles that seen in
    Duchenne. Proximal muscles, especially of the
    lower extremities, are prominently involved. As
    the disease progresses, weakness becomes more
    generalized. Significant facial muscle weakness
    is not a feature. Hypertrophy of muscles,
    particularly in the calves, is an early and
    prominent finding.
  • Most patients with Becker dystrophy first
    experience difficulties between ages 5 and 15
    years, although onset in the third or fourth
    decade or even later can occur. By definition,
    patients with Becker dystrophy walk beyond age
    15, while patients with Duchenne dystrophy are
    typically in a wheelchair by the age of 12.
    Patients with Becker dystrophy have a reduced
    life expectancy, but most survive into the fourth
    or fifth decade.

13
  • Mental retardation may occur in Becker dystrophy,
    but it is not as common as in Duchenne. Cardiac
    involvement occurs in Becker dystrophy and may
    result in heart failure some patients manifest
    with only heart failure. Other less common
    presentations are asymptomatic hyper-CK-emia,
    myalgias without weakness, and myoglobinuria.

14
Laboratory Features
  • Serum CK levels, results of EMG, and muscle
    biopsy findings closely resemble those in
    Duchenne dystrophy. The diagnosis of Becker
    muscular dystrophy requires Western blot analysis
    of muscle biopsy samples demonstrating a reduced
    amount or abnormal size of dystrophin or mutation
    analysis of DNA from peripheral blood leukocytes.
  • Genetic testing reveals deletions or duplications
    of the dystrophin gene in 65 of patients with
    Becker dystrophy, approximately the same
    percentage as in Duchenne dystrophy.

15
Treatment
  • The use of glucocorticoids has not been
    adequately studied in Becker dystrophy.

16
Limb-Girdle Muscular Dystrophy
  • LGMD type 1AD, type2 AR
  • The syndrome of limb-girdle muscular dystrophy
    (LGMD) represents more than one disorder. Both
    males and females are affected.
  • Onset ranging from late in the first decade to
    the fourth decade.
  • typically manifest with progressive weakness of
    pelvic and shoulder girdle musculature.
    Respiratory insufficiency from weakness of the
    diaphragm may occur, as may cardiomyopathy.

17
Emery-Dreifuss Muscular Dystrophy
  • There are two genetically distinct forms of
    Emery-Dreifuss muscular dystrophy (EDMD). One is
    inherited as an X-linked disorder, while the
    other is autosomal dominant
  • Clinically the conditions are closely related. .

18
Clinical Features
  • Prominent contractures can be recognized in early
    childhood and teenage years, often preceding
    muscle weakness. The contractures persist
    throughout the course of the disease and are
    present at the elbows, ankles, and neck.
  • Muscle weakness affects humeral and peroneal
    muscles at first and later spreads to a
    limb-girdle distribution.
  • The cardiomyopathy is potentially life
    threatening and may result in sudden death. A
    spectrum of atrial rhythm and conduction defects
    includes atrial fibrillation and paralysis and
    atrioventricular heart block.

19
Laboratory Features
  • Serum CK may be elevated two- to tenfold.
  • EMG is myopathic.
  • Muscle biopsy shows nonspecific dystrophic
    features.
  • Immunohistochemistry reveals absent emerin
    staining of myonuclei in X-lined EDMD.
  • ECGs demonstrate atrial and atrioventricular
    rhythm disturbances.

20
Treatment
  • Supportive care should be offered for
    neuromuscular disability, including ambulatory
    aids, if necessary. Stretching of contractures is
    difficult. Management of cardiomyopathy and
    arrhythmias (e.g., early use of a cardiac
    pacemaker) may be life saving.

21
Myotonia Congenita
  • Myotonia is the delay of muscle relaxation after
    contraction leading to apparent muscle stiffness.
  • There are two types of Myotonia Congenita
  • Thomsens Disease
  • - AD
  • - Usually presents from birth but
    symptoms may not develop until early childhood.
  • - There is generalized myotonia
    without weakness. Muscle stiffness is enhanced by
    cold and inactivity and relieved by exercise.
  • - Muscle hypertrophy, sometimes
    pronounced.

22
  • Bekers Disease
  • - AR.
  • - Later onset.
  • - There is slight weakness and atrophy
    of distal muscles.
  • Treatment
  • Qunine sulfate, Procainamide, mexilitene,
    and phenytoin.

23
  • Thanks
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