Positional Respiratory Distress in Myasthenic Crisis: A Case of Undiagnosed Thymoma

TL;DR

A patient with myasthenia gravis experienced life-threatening respiratory issues due to an undiagnosed thymoma, highlighting the importance of recognizing positional symptoms in such cases.

Contribution

This case emphasizes the need for clinicians to consider thymoma in MG patients with atypical positional respiratory distress during a crisis.

Findings

Positional respiratory compromise in a myasthenia gravis patient led to the discovery of a large thymoma.

The tumor was found to abut both phrenic nerves, contributing to diaphragmatic dysfunction.

Successful surgical resection required prolonged postoperative support, including tracheostomy and gastrostomy.

Abstract

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder that can present with life-threatening complications, including myasthenic crisis (MC). We present the case of a 52-year-old Hispanic male with known MG who presented to a hospital serving an underserved community with respiratory distress after discontinuing azathioprine. He was initially presumed to be experiencing a typical MC but then exhibited positional respiratory compromise, an inability to tolerate the supine position and the inability to have a nasogastric tube placed, which raised concern for dynamic extrinsic compression of mediastinal structures. These atypical findings prompted imaging, which revealed a large anterior mediastinal mass consistent with thymoma. The patient’s respiratory status worsened when supine, suggesting posture-dependent mass effect likely exacerbated by gravitational forces and impaired diaphragmatic mechanics. The tumor was found to be abutting both phrenic nerves, contributing to diaphragmatic dysfunction and worsening bulbar symptoms. He underwent successful surgical resection but required prolonged postoperative support, including tracheostomy and gastrostomy tube placement. This case highlights the need for heightened clinical suspicion of thymoma in MG patients presenting with crisis, particularly when positional symptoms suggest dynamic mass effect, as early recognition and intervention are essential for optimizing outcomes.

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