Clinical features

The distribution of muscle weakness often has a characteristic pattern.
The cranial muscles, particularly the lids and extraocular muscles, are often involved early in the course of MG, and diplopia and ptosis are common initial complaints.
Facial weakness produces a “snarling” expression when the patient attempts to smile.
Weakness in chewing is most noticeable after prolonged effort, as in chewing meat.
Speech may have a nasal timbre caused by weakness of the palate or a dysarthric “mushy” quality due to tongue weakness.
Difficulty in swallowing may occur as a result of weakness of the palate, tongue, or pharynx, giving rise to nasal regurgitation or aspiration of liquids or food.
In approximately 85% of patients, the weakness becomes generalized, affecting the limb muscles as well.
If weakness remains restricted to the extra ocular muscles for 3 years, it is likely that it will not become generalized, and these patients are said to have ocular MG.
The limb weakness in MG is often proximal and may be asymmetric.
Despite the muscle weakness, deep tendon reflexes are preserved.
If weakness of respiration becomes so severe as to require respiratory assistance, the patient is said to be in crisis.