Atypical presentation of Lambert–Eaton myasthenic syndrome associated with oesophageal squamous cell carcinoma

Lambert–Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction (NMJ) disorder which is categorised as either paraneoplastic or primary autoimmune. In both forms, auto-antibodies target voltage-gated calcium channels at the presynaptic level of the NMJ. Paraneoplastic LEMS is most commonly associated with small cell lung cancer (SCLC), but it can also be caused by other malignancies. We report a rare case of paraneoplastic LEMS associated with oesophageal carcinoma. Over the course of a year, the patient presented with a range of unclear and evolving symptoms, leading to an initial diagnosis of Guillain-Barré syndrome and subsequently Myasthenia Gravis. The diagnosis of LEMS was confirmed serologically, after the discovery of oesophageal cancer, at a stage where treatment options were limited, leading to an unfavourable outcome. This case emphasises the importance of diagnosing LEMS before tumour detection, maintaining suspicion for LEMS in atypical presentations, and thoroughly investigating for malignancies, including extrapulmonary sites.