Emergency use of eculizumab in impending and manifest myasthenic crisis: a retrospective case series

Impending and manifest myasthenic crisis (MC) represent life-threatening neurological emergencies that require immediate intervention. Although eculizumab, a terminal complement C5 inhibitor, has established efficacy in generalized myasthenia gravis, most studies have focused on long-term outcomes, and its potential for rapid onset of effect in acute exacerbations has not been well evaluated. We retrospectively analyzed four acetylcholine receptor (AChR) antibody-positive patients (five acute episodes) who received eculizumab as emergency therapy between January 2024 and July 2025. All patients presented with impending or manifest MC; none had received intravenous immunoglobulin, plasma exchange, or neonatal Fc receptor (FcRn) inhibition within the preceding month. According to the Myasthenia Gravis Foundation of America classification, three patients had class IVb and one had class V. Triggers for exacerbation included COVID-19 infection (<i>n</i> = 2), puerperium (<i>n</i> = 1), PD-1 inhibitor exposure (<i>n</i> = 1), and common infection (<i>n</i> = 1). Within 48 h of eculizumab administration, Quantitative Myasthenia Gravis scores improved from 28.2 ± 4.8 to 15.0 ± 4.1, while Myasthenia Gravis Activities of Daily Living scores decreased from 16.8 ± 2.8 to 6.0 ± 4.3. Notable milestones achieved included arterial blood gas improvement within 7.5 h (one patient), nasogastric tube removal within 48 h (three patients), and successful extubation at 17 h (one patient). No treatment-related adverse events were observed. These preliminary findings suggest that eculizumab may be associated with rapid, temporally related clinical improvement within 48 h with a favorable short-term safety profile in AChR antibody-positive patients with impending or manifest MC, particularly those with complement activation triggers. Larger prospective studies with standardized short-term assessment protocols, including frequent neurological evaluations during the first 48 h, are warranted to further validate its efficacy and define its role as an emergency therapy in the acute management of myasthenic exacerbations.