SHM Converge Scientific Abstract ePoster Gallery-Lying Hidden: Orthopnea Due to Diaphragmatic Paralysis as the Initial Presentation of Myasthenia Gravis

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This case describes a 60-year-old man with hypertension, obesity, and a smoking history who presented with acute shortness of breath that was markedly worse when lying flat (orthopnea). He initially had no obvious limb weakness, sensory changes, or other neurologic deficits, and his cardiac and pulmonary workup was largely unrevealing. Vital signs and labs showed mild hypercapnia but no clear evidence of heart failure, pulmonary embolism, infection, or myocardial injury. Echocardiogram showed normal ejection fraction, and chest CTA was negative. Pulmonary function testing suggested a restrictive ventilatory defect, and bedside respiratory measures showed reduced vital capacity, raising concern for diaphragmatic weakness. Fluoroscopy demonstrated asymmetric elevation and reduced movement of the right hemidiaphragm, consistent with diaphragmatic paresis.<br /><br />After discharge, he developed more classic myasthenic symptoms, including droopy eyelids, intermittent blurred vision, and fatigue with chewing. Acetylcholine receptor antibodies were positive, confirming myasthenia gravis. His presentation was attributed to myasthenia gravis with phrenic neuritis causing diaphragmatic paralysis. He was treated with pyridostigmine and prednisone, then transitioned to mycophenolate and later rituximab due to side effects.<br /><br />The case highlights that orthopnea is not always cardiac in origin. Neuromuscular causes, especially diaphragmatic dysfunction from phrenic nerve involvement, can mimic heart failure. Key diagnostic clues included paradoxical breathing symptoms, restrictive spirometry, reduced inspiratory strength, and fluoroscopic evidence of poor diaphragmatic excursion. The report emphasizes avoiding anchoring bias and maintaining a broad differential diagnosis for orthopnea, since early recognition of myasthenia gravis can lead to timely immunotherapy and improved respiratory outcomes.

Asset Subtitle

Stephan Constante

Meta Tag

Author List Ann Marie Kumfer, Jessica Saganowich, Stephan Constante

Category Clinical Vignettes

Concept Orthopnea

Concept Neuromuscular Respiratory Weakness

Concept Dyspnea

Concept Diaphragmatic Paralysis

Concept Myasthenia Gravis

Distinguished Non-Finalist

Presenter Organization University of North Carolina

Presenting Author Stephan Constante

Track Adult

Keywords

myasthenia gravis

orthopnea

diaphragmatic paralysis

phrenic neuritis

acetylcholine receptor antibodies

restrictive ventilatory defect

hypercapnia

pyridostigmine

prednisone

rituximab

Orthopnea

Neuromuscular Respiratory Weakness

Dyspnea

Diaphragmatic Paralysis

Myasthenia Gravis