Myasthenia gravis presenting as isolated respiratory failure: a case report

Abstract

Myasthenia gravis (MG) is often complicated by respiratory failure, known as a myasthenic crisis. However, most of the patients who develop respiratory symptoms do so during the late course of disease and have other neurological signs and symptoms. However, in some patients respiratory failure is the initial presenting symptom. We report the case of a 68-year-old woman with MG who presented with isolated respiratory failure as her first presenting symptom. As illustrated by this case, it is important to consider neuromuscular disorders in cases of unexplained respiratory failure.

Keywords: Myasthenia gravis; Respiratory insufficiency.

Figure 1

Plain chest radiography. (A) On the first day of the hospital admission, the chest X-ray revealed normal findings except for a focal atelectasis in the right middle lung field. (B) On the sixth day, the chest X-ray showed reduced lung volume.

Figure 2

Spiral computed tomography (CT) scan of the chest. (A) CT scan shows multifocal atelectasis in both lungs. (B) There was no definite evidence of an acute pulmonary thromboembolism.

Figure 3

Electromyography of abductor digiti minimi and orbicularis oculi muscle. (A) These findings demonstrate a decrement in the compound muscle action potential amplitude of about 20% at 2 Hz stimulation at the abductor digiti minimi muscle and (B) more than 70% at 5 Hz stimulation at orbicularis oculi muscle.

Figure 4

The neostigmine test. The patient was on mechanical ventilation; we evaluated the tidal volume after the intramuscular injection of neostigmine. After the neostigmine 10 mg injection, the tidal volume increased from 200 mL/min to 280 mL/min (Servo I, Maquet Medical, Solna, Sweden).