Coexistence of myasthenia gravis and Lambert–Eaton myasthenic syndrome in a small cell lung cancer patient: A case report

RATIONALE: Myasthenia gravis (MG) and Lambert–Eaton myasthenic syndrome (LEMS) are both neuromuscular junction diseases, and some controversy exists whether the 2 diseases occur at the same time. PATIENT CONCERNS: We report a case that a patient with presentation of acetylcholine receptor (AChR) antibody positive MG and LEMS associated with small cell lung cancer (SCLC). DIAGNOSES: The patient firstly suffered from fluctuant symptoms, including slurred speech, double eyelid ptosis, and weakness of limbs. His clinical characteristics were consistent with the diagnosis of MG and were effective with the treatment of pyridostigmine bromide and corticosteroids. After 8 months, the performance of repeated electrical stimulation suggested presynaptic lesion, which supported the patient with LEMS. After further examination, malignant tumors were found in the liver and right lung, and the pathology proved small cell carcinoma. INTERVENTIONS: His clinical characteristics were effective with the treatment of pyridostigmine bromide and corticosteroids. Right hilar lesion and multiple metastatic tumors in liver shrunk after chemotherapy. OUTCOMES: The patient's condition improved gradually. He was followed up for 17 months without tumor progression. LESSONS: The case report illustrates that MG and LEMS may be coexisted in the same patient. In MG and LEMS, clinicians should consider the possibility of malignant tumors as early detection and treatment may significantly improve the patient's prognosis.