Myasthenia gravis is an autoimmune disorder where antibodies are produced against acetylcholine receptors located at the motor end plates in myocardial junctions.
It is very rare, occuring in only about one out of every 1 to 10 million people.It has got equal incidence on both sexes , every ethnicity and all age groups.
I hope you people have heard of Amitabh Bacchan suffering from this dreaded condition.
CLINICAL FEATURES:-
°Age of onset-15-50 years.
°The most evident symptoms is fatigable muscle weakness. Movements are initially strong but rapidly weakens as muscle use continues .
°There is no sensory involvement of the CNS.
°Eye muscles are commonly involved resulting in ptosis and diplopia.
°Weakness in chewing,swallowing,speaking or limb movement occurs.
°Any limb muscle can be involved specially the shoulder girdle.
°Respiratory muscles may involved and respiratory failure is avoidable cause of death.Cough aspiration may occur.
INVESTIGATIONS:-
Tensilon Test-
IV injection of the short acting Anticholinesterase,Edrophonium bromide is used (2mg followed by another 8 mg).There is dramatic improvement of muscle function within 30 seconds and persist for 2-3 minutes.
Positive test is highly suggestive of Myasthenia gravis.
Other tests are-
Chest X-ray
Thyroid function test
Acetyl Choline receptor antibody levels
Anti-MuSK antibody level
Management:-
Goal of treatment is to maximize the activity of acetylcholine at remaining receptors in the neuromuscular junction and to ablosih immune attack.
~Anticholinesterase drug-Pyridostigmine ,Neostigmine are used to prolong the action of acetylcholine.Overdose of these drugs will cause cholinergic crisis.
~Acute treatments- IV immunoglobulins reduces production of antibodies and reduce weakness .
~Plasma exchange-reduces antibody from blood produces mark improvement.
~ Corticosteroid may be used .
~Supportive measures like ventilatory assistance and nasogastric tube feeding may be required in some cases.