2. Myasthenia Gravis
MG is the autoimmune disease
characterised by fluctuating weakness
and rapid fatigue of muscles due to the
breakdown in the normal
communication between nerves and
muscles.
MG is not curable but the symptoms
can be relieved of.

3. Epidemiology :
MG is more common in women younger
than 40 and in men older than 60.
In US, about 14-20 per 100,000
population is affected.
Men are more commonly affected.
Many cases remain undiagnosed.

6. NM Trans. In MG :

7. Pathophysiology :
ANTIBODIES get attached to AchR.
Complement cascade gets activated 
destruction of the junction
Morphology of NM junc. is altered
Hence action potential cannot travel
normally leading to disturbed or absence
in musc. contraction.
Hence, MG occurs as a result of
HYPERSENSITIVITY type 2 reaction.

10. Symptoms :
Weakness of facial muscles - Ptosis,
Diplopia, Diff. in chewing, Dropping of jaw
Weakness of neck muscles - Flexion
Weakness of limb muscles
Weakness of respiratory muscles- Resp.
distress
Severity increases progressively and later
in ends with ATROPHY (burnt – out stage)

15. Thymus in MG :
Unlike normal individuals, there is no
destruction of the T-cells that attacks
one’s own cell and produce
autoantibodies that bind to AchR.
Over functioning of thyroid gland
causes Thymomas(tumor) which are
not cancerous usually.

16. Diagnosis :
Medical history
Physical examination
AChR antibody test. If negative, MuSK antibody
test.
Tensilon test (administer Edrophonium chloride
to relieve weakness temporarily)
Muscle biopsy
Repetitive nerve stimulation.
Single Fiber Electromyography.
CT and MRI of the chest to detect thymoma.

19. Treatment :
No treatment but can be controlled
ACE inhibitors : Pyridostigmine
Corticosteroids : Prednisone
Immunosuppressants : Imuran
Therapy :
Plasmapheresis, Intravenous Ig
Surgery :
Thymectomy

20. CASE STUDY
Mr weld,a 71 year old retired engineer,had been in good health
and active all his life. He developed double vision[diplopia].
Initially, he did not want to seek medical attention because the
double vision sometimes improved spontaneously. however, it
gradually worsened over the course of 4 months and he finally
scheduled an appointment with his physician.
On examination,the doctor noticed that Mr weld had ptosis of
both eyelids so that they covered the upper third of the irises
of his eyes.When the doctor asked Mr weld look to the right
and then to the left, he noticed limitations in the ocular
movements of both eyes.
The remainder of the neurological examination was normal.

21. No other muscle weakness was found during the examination.A
radiological examination of the chest was performed,and it was
normal.There was no evidence in the radiograph of enlargement
of the tymus gland. A blood sample was taken from Mr weld,and
his serum was tested for antibodies against the acetylcholine
receptor.The serum contained 6.8 units of antibody against the
acetylcholine receptor[normal less than 0.5 units].Mr weld was
told to take Pyridostigmine,and this limited the amount he could
take.
Three years later, Mr weld developed a severe respiratory
infection.Soon afterward,his ptosis became so severe that he had
to lift his eyelids by taping them with adhesive tape. His diplopia
recurred and his speech became indistinct. he developed difficulty
in chewing and swallowing food. He could only tolerate a diet of
soft food and it would take him several hours to finish a meal

22. On examination the neurologist noted that Mr weld now had
weakness of the facial muscles and the tougue, and the
abnormality in ocular movements again became apparent.Because
of the dairrhea Mr weld was only able to tolerate one-quarter of
the prescribed dose of pyridostigmine. He also developed difficulty
in breathing. His vital capacity{the amount of air he could exhale
in one deep breath} was low,at 3.5 liters.
He was admitted to hospital and treated with azathioprine.
Thereafter he showed steady improvement. His ptosis and
diplopia improved remarkably and he was able to eat normally.His
vital capacity returned to normal and was measured to be 5.1
liters