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Persistent pediatric asthma — USMLE Step 3 MCQ

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HardPediatricsPersistent pediatric asthmaUSMLE Step 3

A 58-year-old with myasthenia gravis and pneumonia develops dysphagia, weak cough, paradoxical breathing, vital capacity 12 mL/kg, and negative inspiratory force -18 cm H2O. Oxygen saturation is 96% on nasal oxygen. Which management is most appropriate?

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Correct answer: A — Intubate and begin plasma exchange or intravenous immunoglobulin

The best answer is “Intubate and begin plasma exchange or intravenous immunoglobulin”. Bulbar weakness and severely impaired respiratory mechanics indicate myasthenic crisis despite a preserved saturation, which can fall late. Controlled intubation plus rapid immunomodulation is needed. Pyridostigmine alone is inadequate and magnesium can worsen transmission. The alternatives are less suitable because they mistime the intervention, omit a necessary component, or apply treatment for a different physiologic problem; the stem's decisive findings determine the sequence.

Reference: International Consensus Guidance for Myasthenia Gravis: https://pmc.ncbi.nlm.nih.gov/articles/PMC7884987/