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Liu et al. Developing treatment guidance for myasthenia gravis

than delayed thymectomy; (D) for seronegative myasthenic weakness requiring intubation or non-
children, there is always a risk that some will have a invasive ventilation to avoid intubation”. The concept of
CMS and not immune-mediated JMG; (E) evaluation “impending myasthenic crisis” will raise the awareness
at a centre specializing in childhood neuromuscular of the physicians who can take proactive approach to
diseases should be considered before recommending intervene before crisis actually takes place. [12]
thymectomy in young patients with seronegative MG.”
Another concept is refractory MG. It is defined as
Round 2 votes: median 8, range 2-9, 4 panelists rated “PIS is unchanged or worse after corticosteroids and
2-4, and the rest in the 7-9 range. There was still a at least 2 other IS agents, used in adequate doses
disagreement, no consensus. for an adequate duration, with persistent symptoms
or side effects that limit functional, as defined patient
Round 3 statements (modified based on discussion): and physician.” Refractory MG has been the focus of
“(A) the value of thymectomy in the treatment of pre- several discussions, [13,14] although without a specific
pubertal MG patients is unclear, but thymectomy definition until the 2016 Guidance. The definition
should be considered in children with generalized of refractory MG could be furthered developed and
AChR ab MG either if: the response to AChE inhibitor improved, however the one currently approved
-
+
and immunosuppressive is unsatisfactory, or If there provides a common denominator for MG specialists.
is a need/desire to avoid potential complications of
immunosuppressive therapy; (B) for children diagnosed Guideline topics
as seronegative GMG, the possibility of a congenital The consensus guidance treatment statements were
myasthenic syndrome or other neuromuscular developed around the following seven major topics:
condition should be entertained, and evaluation at a symptomatic and IS treatment of MG, IVIg and PLEX,
center specializing in neuromuscular diseases is of impending and manifest crisis, thymectomy in MG,
value prior to thymectomy.”
juvenile MG, MG with MuSK antibodies and MG in
Round 3 votes: median 8, range 7-9, appropriate with pregnancy. The following four topics require further
discussions.
consensus.
Symptomatic and IS treatment of MG
Final statement on the publication: “(A) the value of
thymectomy in the treatment of pre-pubertal patients The statement on the use pyridostigmine is straight-
with MG is unclear, but thymectomy should be forward and relatively easy to reach consensus. It is
considered in children with generalized AChRantibody- almost always the first choice in treating MG patients.

positive MG. (a) if the response to pyridostigmine and However, when pyridostigmine is not readily available
IS therapy is unsatisfactory; or (b) in order to avoid due to various social-economical reasons (for example
potential complications of IS therapy. (B) For children in recent months in mainland China), physician may
diagnosed as seronegative generalized MG, the directly prescribe nonsteroidal IS agents.
possibility of a congenital myasthenic syndrome or other
neuromuscular condition should be entertained, and We totally agree with the statements on the use of IS
evaluation at a center specializing in neuromuscular treatment, especially statement 5 on IS agent dosage
diseases is of value prior to thymectomy.” and duration of treatment. It is highly desirable to
prescribe a low dose of corticosteroids and dosage
DISCUSSION adjustments should not be made too frequently and
abruptly (“no more frequently than every 3-6 months”)
Preliminary definitions based on our decades of clinical experience in China,
Among the preliminary definitions compiled for the although there are very different views and approaches
2016 International Consensus Guidance for MG, for regarding dosage and duration of treatment among
the first time two concepts are given clear definitions Asian physicians. [8,15,16]
and provide highly valuable guidance to the clinical
practice of treating MG patients. IVIg and PLEX
Although the guidance was developed with a priori
The first concept is impending myasthenic crisis. It agreement of not considering treatment costs and
is defined as “Rapid clinical worsening of MG that, availability, it is worth noting that IVIg and PLEX are
in the opinion of the treating physician, could lead to not covered by the Chinese insurance system. Since
crisis in the short term (days to weeks).” In the past, they are both expensive procedures (about $4,400-
crisis in MG is only referred to as manifest myasthenic $7,300/IVIg and $1,500/PLEX), their applications
crisis, defined as “MGFA Class V Worsening of have been limited.
58 Neuroimmunology and Neuroinflammation ¦ Volume 4 ¦ March 30, 2017