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• Antibodiesattack Acetylcholine(ACH) receptorsat the
motor end plate
• Decreased number of (ACH) receptor sitesat
• Preventsneurotransmitter (ACH) from attaching and
• Resulting in lossof musclestrength
• No singlecausehasbeen identified
• Abnormal thymustissuefound in most
• Thymic tumorsfound in 15% of
• Virusinfectionshavebeen found in
somecasesand areasuspected cause
• MyastheniaGravisisnot agenetically inherited disease
• Somefamiliesappear to carry agenethat increasesthe
risk for developing thedisease
• No specific genehasbeen identified and thereareno tests
for genetic screening
Signs and Symptoms
• Affectsany of themusclesthat can be controlled
voluntarily, certain musclegroupsaremorecommonly
affected than others
• Eye, face, throat, neck, limb muscles
• Difficulty speaking (dysarthria)
• Difficulty swallowing (dysphagia),
• Drooping eyelids(ptosis)
Signs and Symptoms
• Doublevision (diplopia)
• Nasal-sounding speech and weak neck musclesthat give
thehead atendency to fall forward or backward.
• Symptomstend to progressover time, usually reaching
their worst within afew yearsafter theonset of the
• Worsening muscleweaknesswith repeat activity
Myasthenic crisis: A life-threatening condition, which occurs
when the muscles that control breathing become too weak
to do their jobs. Emergency treatment is needed to provide
mechanical assistance with breathing. Medications and
blood-filtering therapies help people recover from
myasthenic crisis, so they can again breatheon their own.
Thymus tumors: About 15 percent of the people who have
myasthenia gravis have a tumor in their thymus, a gland
under the breastbone that is involved with the immune
system. Most of thesetumorsarenoncancerous.
Underactive or overactive thyroid: The thyroid gland,
located in the neck, secretes hormones that regulate
metabolism. If thyroid is underactive, body uses energy more
slowly. An overactive thyroid makes body use energy too
Lupus: Disease of immune system. Common symptoms
include painful or swollen joints, hair loss, extreme fatigue
and ared rash on theface.
Rheumatoid arthritis: Caused by problems with immune
system. It is most conspicuous in the wrists and fingers, and
can result in joint deformities that make it difficult to use
• Chronic diseasewith periodsof exacerbation and
• Diseasecourseishighly variable
• Symptomsrespond well to treatment and in most cases
thepatient can liveanormal or nearly normal life
• Ocular Myastheniahasthebest prognosis
Edrophonium test: Injection of the chemical
edrophonium (Tensilon) may result in a sudden,
although temporary, improvement in muscle
strength — an indication that you may have
myasthenia gravis. Edrophonium acts to block an
enzyme that breaks down acetylcholine, the
chemical that transmits signals from nerve
endingsto musclereceptor sites.
Blood analysis: A blood test may reveal the
presenceof abnormal antibodies that disrupt
the receptor sites where nerve impulses
signal musclesto move.
Repetitive nerve stimulation: Is a type of
nerve conduction study, in which electrodes are
attached to skin over the muscles to be tested. Small
pulses of electricity are sent through the electrodes to
measure the nerve's ability to send a signal to muscle.
To diagnose MG, the nerve will be tested many times
to see if its ability to send signals worsens with
Single-fiber electromyography (EMG):
EMG measures the electrical activity traveling
between brain and muscle. It involves inserting a very
fine wire electrode through skin and into a muscle. In
single-fiber EMGs, asinglemusclefiber istested.
Imaging scans: CT scan or an MRI to confirm a
tumor or other abnormality in thymus.
Thymectomy - surgical removal of the
thymusgland. Theroleof thethymusgland in
MG isnot fully understood, and thethymectomy
may or may not improveapatient'ssymptoms.
Plasmapheresis- aprocedurethat removes
abnormal antibodiesfrom theblood and replaces
thepatient'sblood with normal antibodies
through donated blood.
Extent of theproblemsisdependent on the
severity of thecondition and thepresenceof other
problemsthat could affect thepatient.