Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.
Treatment follows a stepwise logic: first make more acetylcholine available, then suppress the immune attack, then remove the thymus that sustains it, and finally, for refractory disease, deploy targeted biologics that clear antibodies or delete the cells producing them.
Symptom control with acetylcholinesterase inhibitors
Pyridostigmine is first-line for all patients. A typical oral dose is 60 mg every 4 hours, adjustable upward, with onset in 30–60 minutes and effect lasting 3–4 hours; parenteral forms serve perioperative and crisis use. Neostigmine, given every 4–6 hours and usually parenterally, is the acute backup rather than the chronic oral agent.
These drugs improve strength without touching the disease itself, and they have a ceiling: when few receptors remain, higher doses add cholinergic side effects (diarrhoea, cramps, salivation, bronchial secretions) without meaningful strength gains. High-dose weakness from excess acetylcholine (cholinergic crisis) can be clinically difficult to distinguish from myasthenic worsening, so escalation beyond roughly 90–120 mg per dose without benefit should prompt a change of strategy rather than further increases.
Immunosuppression
When symptom control alone fails, corticosteroids come first, usually prednisone or prednisolone started at a low dose such as 0.5 mg/kg/day and increased gradually toward the lowest effective maintenance dose. Gradual introduction matters because a sudden high dose can transiently worsen weakness before improvement begins. Younger patients generally tolerate the steroid burden better.
Azathioprine is the usual steroid-sparing second line, at a minimum effective dose around 2 mg/kg/day, allowing the steroid taper. Its full effect takes 3–6 months, so it is started with overlap rather than as a rescue agent. The practical escalation runs from pyridostigmine alone, to added low-dose steroid when symptoms such as diplopia persist, to azathioprine or thymectomy consideration in refractory or maintenance phases (Sanders et al., 2016; Narayanaswami et al., 2021).
Thymectomy
Thymectomy removes the site where receptor-directed T cells are activated and B cells are driven toward antibody production. Thymoma makes removal mandatory, since these tumours can invade locally. In non-thymomatous generalised disease, a randomised trial showed thymectomy plus prednisone lowered quantitative weakness scores by a clinically significant margin (about 2.3 points on the quantitative scale) and reduced steroid requirements compared with prednisone alone (Wolfe et al., 2016). Benefit is most firmly established in acetylcholine-receptor-positive disease; in MuSK-positive disease, where pathology is not thymus-driven, thymectomy is generally not recommended.
Targeted biologics for refractory disease
Eculizumab, a monoclonal antibody against complement, blocks the complement-mediated destruction of the endplate, one of the three injury mechanisms alongside receptor degradation and blockade. It is reserved for refractory generalised receptor-positive disease (Howard et al., 2017). Because complement inhibition removes a key defence against meningococci, vaccination against Neisseria meningitidis beforehand is a non-negotiable safety requirement.
Neonatal Fc receptor (FcRn) blockers, efgartigimod and rozanolixizumab, work differently: FcRn normally rescues IgG from degradation and recycles it, giving antibodies their roughly 3-week half-life. Blocking the receptor accelerates clearance of all IgG, including pathogenic antibodies, with faster onset than azathioprine at the cost of high expense and broader infection susceptibility from lowered protective antibodies (Howard et al., 2021).
Rituximab, an anti-CD20 antibody that depletes B cells, is particularly effective in MuSK-positive disease, where B-cell-driven antibody production dominates, and is increasingly used in refractory receptor-positive cases without being first-line there.
Myasthenic crisis
Crisis means an exacerbation severe enough to require ventilatory support. Infection is the commonest trigger, followed by treatment taper or non-adherence, surgery or physiological stress, and newly introduced worsening drugs. Management starts with the airway: intubate on clinical trajectory rather than waiting for blood gases to collapse. Plasma exchange, typically 4–6 sessions, removes circulating antibodies with rapid but temporary effect; intravenous immunoglobulin is the immunomodulatory alternative. Cholinesterase inhibitor dosing is adjusted cautiously, mindful of the cholinergic-crisis ambiguity above.
Medicines that can worsen weakness
Several drug classes are reported to impair neuromuscular transmission and deserve a check before prescribing: aminoglycosides, macrolides, and fluoroquinolones among antibiotics; beta-blockers; magnesium, which competes with calcium at the nerve terminal; neuromuscular blocking agents, to which these patients are exquisitely sensitive; and penicillamine, which can induce the disease de novo (Sanders et al., 2016). These are reasons for caution and substitution, not absolute prohibitions in every setting.
Severity guides intensity
Roughly mapping the classification in Myasthenia Gravis:
- Ocular-only disease often rests on pyridostigmine, with or without low-dose steroid.
- Mild generalised disease adds corticosteroids.
- Moderate disease adds azathioprine and thymectomy consideration.
- Severe and bulbar-predominant disease brings aggressive immunosuppression with crisis precautions.
- Intubated disease means full crisis management.
Ocular disease stable for about 2 years usually stays ocular, but the rule is statistical, not absolute.
Evidence anchors
- Sanders DB, Wolfe GI, Benatar M, et al. International consensus guidance for management of myasthenia gravis. Neurology. 2016;87(4):419-425. doi:10.1212/WNL.0000000000002790
- Narayanaswami P, Sanders DB, Wolfe G, et al. International consensus guidance for management of myasthenia gravis: 2020 update. Neurology. 2021;96(3):114-122. doi:10.1212/WNL.0000000000011124
- Wolfe GI, Kaminski HJ, Aban IB, et al. Randomized trial of thymectomy in myasthenia gravis. N Engl J Med. 2016;375(6):511-522. doi:10.1056/NEJMoa1600403
- Howard JF Jr, Utsugisawa K, Benatar M, et al. Safety and efficacy of eculizumab in anti-acetylcholine receptor antibody-positive refractory generalised myasthenia gravis (REGAIN). Lancet Neurol. 2017;16(12):976-986. doi:10.1016/S1474-4422(17)30369-1
- Howard JF Jr, Bril V, Vu T, et al. Safety, efficacy, and tolerability of efgartigimod in patients with generalised myasthenia gravis (ADAPT). Lancet Neurol. 2021;20(7):526-536. doi:10.1016/S1474-4422(21)00159-4