Rationale: The Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular disease; its unique symptoms of LEMS include dry mouth with a metallic taste, constipation, and erectile dysfunction. As it is quite rare, isolated ocular muscle impairment associated with LEMS east to ignore.
Patient concerns: A 65-year-old man presented with alternating ptosis and diplopia. Isolated ocular muscle impairment had lasted for 6 years, and the patient was initially diagnosed with ocular myasthenia gravis (MG). Treatment with azathioprine only slightly improved symptoms over the first 2 months; long-term treatment was not effective.
Diagnoses: Dynamic observation of chest computed tomography images revealed a slowly progressing nodule in the lower lobe of the left lung. The subsequent pathologic examination following mass resection confirmed a diagnosis of lung adenocarcinoma.
Interventions: The patient was ultimately diagnosed with the Lambert-Eaton myasthenic syndrome associated with pulmonary adenocarcinoma.
Outcomes: Resection of the lung tumor relieved all symptoms.
Lessons: Other causes of ocular MG symptoms should be considered when standard MG therapy is ineffective, especially the Lambert-Eaton myasthenic syndrome.