Successful treatment of advanced lung adenocarcinoma complicated with Lambert‐Eaton myasthenic syndrome: A case report and literature review

Lambert‐Eaton myasthenic syndrome (LEMS) is a rare disease characterized by involvement of the neuromuscular junction. Most cases have an underlying malignancy, especially small‐cell lung cancer (SCLC), while adenocarcinoma is less common. Here, we report a rare case of metastatic lung adenocarcinoma complicated with LEMS. In this case, L858R mutation was detected in the 21st exon of the EGFR gene. First‐line treatment with gefitinib was given, and the patient has survived for more than six years. Early diagnosis of LEMS and timely and effective treatment can result in a good prognosis. We also searched for “lung cancer”, or “carcinoma of lung”, or “adenocarcinoma of lung”, or “Lambert‐Eaton myasthenic syndrome” in PubMed until 1 December 2019. Seven cases of lung adenocarcinoma complicated with LEMS were found, most of which had a poor prognosis. KEY POINTS: This article reports a rare case of metastatic lung adenocarcinoma with EGFR mutation, complicated with LEMS. Gefitinib was given as first‐line treatment, and resulted in a good prognosis.