ABSTRACT
The clinical onset is usually slow and progressive over 5 years or more, but it can occasionally follow a fulminant course. There can be periods of remission of up to 3 years. Clinically, it presents as a muscular weakness characterized by fatiguability after repetitive or sustained contraction. It is most marked in the face and eyes, producing diplopia and ptosis. Speech and swallowing become affected and there may be a proximal upper limb weakness. The lower limbs are affected last. The greatest danger is the involvement of the ventilatory muscles (this may be very insidious) and bulbar palsy. In myasthenia crisis, ventilatory function should be monitored as in the Guillain-Barré syndrome (see page 932). Rarely, there is a cardiomyopathy.
