Paraneoplastic Lambert-Eaton myasthenic syndrome: a diagnostic challenge

Abstract

Lambert-Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disorder. Underlying small cell lung cancer is found in more than half of patients. Proximal muscle weakness, autonomic features and areflexia are typical manifestations. However, LEMS is often misdiagnosed. We report a rare case of paraneoplastic LEMS, identified amid admission due to a different diagnosis. Our patient was initially admitted due to aspiration pneumonia. Further investigation revealed clinical and electrophysiological manifestations of LEMS. High clinical suspicion and early diagnostic workup were paramount in the patient outcome. Nevertheless, paraneoplastic aetiology was difficult to confirm and revealed itself a difficult challenge. Clinical awareness is crucial to diagnose LEMS and urge cancer screening and early treatment.

Keywords: Lung cancer (oncology); Neuromuscular disease.

Figure 1

Electromyography displaying a typical Lambert-Eaton myasthenic syndrome pattern. (A) Left trapezius muscle—20 Hz high-frequency stimulation of the homolateral accessory nerve resulting in 74% and 43% incremental response in CMAP amplitude and area, respectively. (B) Left fifth finger abductor muscle—30 Hz high-frequency stimulation of the homolateral cubital nerve resulting in 225% and 89% incremental response in CMAP amplitude and area, respectively. CMAP; compound muscle action potential.

Figure 2

(A) CT of the thorax at the time of admission, showing 9 mm subpleural, perivertebral, in the right inferior pulmonary lobe. (B) Six-month follow-up CT, showing a 35 mm (long axis), heterogenous lesion in the right hilum, non-existing in previous exams.