Myasthenia gravis primary prevention

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

No proven strategy exists to prevent the initial development of myasthenia gravis (MG), an autoimmune disorder of unclear inciting cause. However, certain medications are recognized to trigger new-onset (de novo) MG or unmask subclinical disease, and awareness of these agents, particularly immune checkpoint inhibitors (ICIs), is the main practical form of risk reduction of MG.

There are no established measures that prevent the onset of MG. Prevention efforts are therefore limited to avoiding or cautiously using drugs capable of provoking de novo disease. The 2020 MGFA guidance identifies several agents that can precipitate MG in previously unaffected individuals, including D-penicillamine (strongly linked to drug-induced MG), chloroquine and hydroxychloroquine, and immune checkpoint inhibitors used in cancer therapy. Where clinically feasible, these agents should be used only when necessary, with monitoring for emerging neuromuscular symptoms.^[1]

ICIs targeting CTLA-4 (ipilimumab), PD-1 (nivolumab, pembrolizumab, cemiplimab), and PD-L1 (atezolizumab, durvalumab, avelumab) can trigger new-onset MG, with reported frequencies of roughly 0.1–0.2% among patients on PD-1 inhibitors. ICI-associated MG tends to appear early in treatment, is frequently severe with a high rate of respiratory crises, and may overlap with myositis and myocarditis. To reduce risk and enable early detection, the guidance advises:

• Counseling candidates for ICI therapy about the possibility of MG and other immune-related neurologic complications before treatment begins.
• Close clinical surveillance, especially of respiratory and bulbar function, during therapy so that emerging weakness is recognized promptly.
• There is currently insufficient evidence to recommend routine AChR antibody testing before starting ICIs in patients without known MG.^[1]

Because immunosuppressive therapy is central to MG management, live-attenuated vaccines are contraindicated once immunosuppression is under way. Ensuring appropriate immunization before immunosuppression, and following ACIP or local vaccination guidance, is relevant to preventing infectious complications rather than MG itself.^[1]

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