Mysasthenia Gravis

#med #disease #y2023

Presentation :

Ptosis or diplopia (first manifestation in most patients), muscle weakness, including dysphagia and dyspnea
DDx includes:
- Botulism: starts with cranial nerve involvement, including diplopia, dysphagia, and sluggish or nonreactive pupils, whereas the pupils are normal in MG
- Lambert-Eaton Myasthenic Syndrome: progressive proximal weakness and diminished tendon reflexes that transiently improve with repetitive movement of affected muscles

caused by antibodies directed against the acetylcholine receptor, which results in impaired neuromuscular transmission

Single-fiber EMG can establish the diagnosis
Positive anti–acetylcholine receptor antibody titer (found in 90% of patients; negative titer does not rule out MG)
Perform CT of the chest to detect thymoma
Check TSH because of the association of MG with autoimmune thyroid disorders.

Pyridostigmine is the initial therapy.
Thymectomy is indicated if a thymoma is found on imaging
In patients with active disease <65y and within 3y of diagnosis, can consider thymectomy to (potentially) avoid or minimize immunotherapy.
Myasthenic crisis and refractory disease should be treated with plasmapheresis or IV immune globulin.
- Pyridostigmine monotherapy should be avoided in patients with myasthenic crisis because the drug increases respiratory secretions