Myasthenia gravis secondary prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Hafiz M. Ahmed, M.D.[2]

No formal secondary-prevention program exists for myasthenia gravis (MG). In practical terms, however, once MG is established, efforts to prevent worsening, exacerbations, and myasthenic crisis are important, and the 2020 Myasthenia Gravis Foundation of America (MGFA) International Consensus Guidance provides guidance most relevant to this goal, principally avoidance of drugs that aggravate MG, precautions with immune checkpoint inhibitors (ICIs), and required vaccination before complement-inhibitor therapy.

There are no formally established measures for the secondary prevention of MG. Preventive care therefore focuses on reducing the risk of clinical deterioration in patients with known disease.^[1]

Numerous medications can aggravate MG or precipitate crisis, and awareness of them is central to preventing exacerbations. Agents with the strongest evidence for worsening MG include:

• Certain antibiotics, aminoglycosides, fluoroquinolones (which carry an FDA boxed warning), macrolides, and telithromycin (which should not be used in MG at all).

• Cardiovascular drugs such as beta-blockers and procainamide.
• Magnesium, particularly when given intravenously.
• Antimalarials (chloroquine, hydroxychloroquine) and D-penicillamine.
• Botulinum toxin, quinine, iodinated contrast media, statins, and deferoxamine.

These drugs need not be absolutely prohibited; reported associations are sometimes rare or coincidental. Decisions should weigh the individual risk–benefit balance, use alternatives where possible, and include monitoring for worsening when an implicated drug is necessary.^[1]

In patients with preexisting MG who require cancer immunotherapy, well-controlled disease is not an absolute barrier to ICI use, but steps to limit deterioration are advised: avoiding combined CTLA-4 plus PD-1/PD-L1 regimens because of the greater risk of severe immune-related events, monitoring respiratory and bulbar function closely, and continuing MG-directed treatment throughout. Should overt MG emerge or flare during therapy, prompt high-dose corticosteroids together with plasma exchange or IVIG may be required, and the decision to stop the ICI depends on the oncologic situation.^[1]

Because eculizumab increases susceptibility to meningococcal infection, meningococcal immunization (both conjugate ACWY and serogroup B vaccines) is required at least two weeks before initiating therapy. If treatment must begin sooner, antibiotic prophylaxis should be provided and continued for at least two weeks after vaccination. ACIP or local immunization recommendations should be followed.^[1]

Starting corticosteroids can transiently worsen MG within the first two weeks, occasionally precipitating crisis. Careful monitoring during initiation, and consideration of gradual dose escalation or inpatient observation in patients with bulbar or respiratory involvement, helps prevent steroid-induced deterioration.^[1]

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