The usual initial complaint is a specific muscle weakness rather than generalized weakness
Extraocular muscle weakness or ptosis is present initially in 50% of patients and occurs during the course of illness in 90%
The disease remains exclusively ocular in only 16% of patients
Rarely, patients have generalized weakness without ocular muscle weakness
Bulbar muscle weakness is also common, along with weakness of head extension and flexion
Limb weakness may be more severe proximally than distally
Isolated limb muscle weakness is the presenting symptom in fewer than 10% of patients
Weakness is typically least severe in the morning and worsens as the day progresses
Weakness is increased by exertion and alleviated by rest
Weakness progresses from mild to more severe over weeks or months, with exacerbations and remissions
Weakness tends to spread from the ocular to facial to bulbar muscles and then to truncal and limb muscles
About 87% of patients have generalized disease within 13 months after onset
Less often, symptoms may remain limited to the extraocular and eyelid muscles for years
The following factors may trigger or worsen exacerbations:
Bright sunlight