Prevalence 0.5 - 4 per 100000 population
Acute disease, not chronic, unlike DMD
due to immune response to foreign agents (usually infectious agents) and then body owns immune response is mistargeted at own host cells instead of foreign antigen
Respiratory tract or gastric infection often precedes the onset of symptoms
Immunisation and surgery may also be precipitating factors
Autoimmune disorder affecting the peripheral nerves