Myasthenia Gravis with Worsening Bulbar Symptoms: When to Escalate
A 41-year-old woman with generalized myasthenia gravis (AChR antibody positive) on pyridostigmine 60 mg four times daily and prednisone 10 mg daily presents with 5 days of worsening double vision, nasal speech, and difficulty swallowing solids. She has no fever, no cough, and no shortness of breath at rest. Exam: ptosis and fluctuating diplopia, nasal voice, weak palate elevation, and neck flexion 4/5. FVC is 70% predicted, NIF -45 cmH2O, and single-breath count is 28. She was started on azathioprine 3 weeks ago. She asks to go home and 'ride it out.'
1. How do the respiratory measurements and bulbar findings inform disposition, and what is the argument against discharge home?
Read the worked answer
The measurements are reassuring in isolation but not sufficient to justify discharge in the setting of active bulbar worsening.
Reasoning:
- FVC 70% predicted and NIF -45 cmH2O are above the thresholds generally used to flag impending respiratory failure (roughly FVC <20 mL/kg or <1 L, NIF weaker than about -30 cmH2O, or a rapidly declining trend). Single-breath count of 28 is also not frankly abnormal.
- However, bulbar weakness (nasal speech, weak palate, dysphagia for solids) is a major risk factor for aspiration and for subsequent respiratory compromise, and these can deteriorate quickly. The trajectory over 5 days is the concern: the patient is worsening despite current therapy.
- Azathioprine started 3 weeks ago has not yet reached therapeutic effect (typically 3-6 months), so she is effectively on inadequate immunosuppression during a flare.
- Discharge home with active bulbar worsening risks aspiration pneumonia, which can precipitate a myasthenic crisis.
Disposition: admit for monitoring, serial FVC/NIF and single-breath counts, swallow evaluation, and escalation of therapy. Do not discharge home to 'ride it out.'
2. What treatment escalation would you choose, and how do you sequence it given that she is already on prednisone and a recently started steroid-sparing agent?
Read the worked answer
The patient is in a worsening bulbar flare with inadequate immunosuppression, so escalation is warranted.
Options and sequencing:
- IVIG or plasma exchange are the standard rapid-acting options for moderate-to-severe exacerbations and impending crisis. Either can be used; choice depends on availability, comorbidities, and prior response. IVIG is often first-line for convenience; PLEX may be preferred in severe or refractory cases.
- Corticosteroids: she is already on low-dose prednisone. Increasing the dose can improve myasthenia but carries a risk of transient early worsening, so any increase should occur in a monitored setting, not as an outpatient adjustment.
- Continue and optimize the steroid-sparing agent (azathioprine), but recognize it will not act for weeks to months. Check thiopurine methyltransferase status and monitor for toxicity if not already done.
- Consider rituximab or other agents if she is refractory, particularly if MuSK antibody positive (not established here) or if response to standard therapy is inadequate.
- Supportive care: swallow evaluation, aspiration precautions, and monitoring for respiratory failure.
Sequencing: admit, start IVIG or PLEX promptly while continuing azathioprine, and consider a monitored increase in corticosteroid dose. Do not rely on the recently started azathioprine for acute control.