When IVIG Is Not Enough: Plasma Exchange Rescue in Myasthenic Crisis

Introduction

Myasthenic crisis is a life-threatening exacerbation of myasthenia gravis (MG) characterized by respiratory or bulbar weakness requiring ventilatory support. Infection is a common precipitant. Intravenous immunoglobulin (IVIG) and plasma exchange (PLEX) are the main rapid immunomodulatory therapies. Although comparative trials suggest broadly similar efficacy, expert consensus suggests that PLEX may act more rapidly and may be more effective in severe crisis. When clinical deterioration occurs despite recent IVIG, prompt reassessment and transition to an alternative rescue strategy may be warranted.

Case Presentation

An 80-year-old man with longstanding MG, dysphagia, obstructive sleep apnea, hypertension, hyperlipidemia, and heart failure with preserved ejection fraction presented with worsening fatigue, generalized weakness, blurred vision, dysphagia, and dyspnea shortly after a hospitalization for an MG exacerbation treated with IVIG. Although he initially improved following IVIG, his symptoms recurred after discharge, prompting readmission. During hospitalization, he developed rapidly progressive respiratory distress and hypoxemia requiring emergent endotracheal intubation. Neurologic examination demonstrated ptosis and persistent weakness, and his deterioration was considered consistent with myasthenic crisis. Chest CT demonstrated extensive secretions filling the left lower-lobe bronchus with complete left lower-lobe atelectasis and additional right lower-lobe mucus plugging. Urine culture grew greater than 100,000 CFU/mL of Pseudomonas aeruginosa, representing a potential infectious contributor to his exacerbation without documented sepsis. Given recurrent respiratory and bulbar symptoms despite recent IVIG and a history of favorable response to plasmapheresis, the treatment strategy was changed to PLEX. Nephrology initiated a planned five-treatment course. After the first plasma exchange, his respiratory status improved sufficiently for extubation the following day, with good respiratory effort and continued clinical improvement. Subsequently, he was sitting in a chair, reported symptomatic improvement, and demonstrated a negative inspiratory force of approximately −50 cm H₂O and vital capacity of 1.3 L while receiving low-flow supplemental oxygen.

Discussion

This case highlights the importance of reassessing the therapeutic approach when myasthenic crisis progresses despite recent IVIG. Although IVIG and PLEX are both accepted rescue therapies, inadequate response to one modality should not preclude timely use of the other when respiratory or bulbar weakness continues to worsen. Limited prior evidence describes successful PLEX rescue after IVIG failure, and in this patient, transition to PLEX was followed by rapid respiratory improvement and extubation. The case also illustrates the multifactorial nature of respiratory deterioration in MG, in which infection, impaired secretion clearance, atelectasis, and neuromuscular weakness may coexist. Management requires identification and treatment of potential precipitants alongside disease-directed therapy. Serial respiratory mechanics may assist in monitoring but should be interpreted in clinical context, particularly in patients with bulbar weakness. Early recognition of treatment failure and timely escalation to an alternative rescue therapy may reduce the morbidity associated with prolonged myasthenic crisis.