Table 1.

Commonly used definitions for refractory MG (adapted from Mantegazza and Antozzi⁷).

Number	Definition	Attributes
1	Failure to respond adequately to conventional treatment	Insufficient response (e.g. persistent moderate to severe weakness) to maximal safe doses of steroids and at least one immunosuppressive drug at adequate dose and duration, with sufficient symptomatic treatment
2	Inability to reduce immuno-suppressive therapy without clinical relapse or need for ongoing rescue therapy (e.g. IVIg or PE/IA)	Possible sufficient initial response to immuno-suppressive therapy; however, the duration of such therapies has to be restricted owing to the potential for profound side effects associated with their use (particularly in the case of corticosteroids)
3	Severe or intolerable adverse effects from immunosuppressive or symptomatic therapy	More accurately described as ‘treatment intolerant’; however, the inability to effectively treat MG using conventional immunosuppressive agents has the same result as being treatment refractory
4	Comorbid conditions restricting use of conventional therapies	Again, ‘treatment intolerant’
5	Frequent myasthenic crises even while on immunosuppressive and symptomatic therapy	Life-threatening events, characterized by respiratory or bulbar weakness, or paralysis requiring urgent hospitalization

IA, immunoadsorption; IVIg, intravenous immunoglobulin G; MG, myasthenia gravis; PE, plasma exchange.