Background:
Lambert-Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disorder. This disorder can manifest due to a paraneoplastic syndrome or a primary autoimmune disorder. The majority of cases are associated with small-cell lung cancer, but has also been observed with other cancers. Clinical presentation can be subtle and progressive, making diagnosis a challenge. It is important to focus on the prominent clinical symptom of muscle weakness,  as this is the primary clinical symptom ( muscle weakness). The underlying pathophysiology involves the development of antibodies that target voltage-gated calcium channels (VGCCs) on presynaptic nerve terminals, resulting in reduced acetylcholine (ACh) neurotransmitter release.  (1)  (2)(3)

Case Presentation:
We report the case of a 73-year-old woman presenting with a three-year history of generalized weakness, progressive fatigue, significant weight loss, dry eyes and mouth, leg aches, and increasing difficulty performing activities of daily living. She denied changes in bowel or bladder function, although she reported symptoms of overactive bladder for which she was taking Solifenacin. Neurological examination revealed preserved muscle bulk and tone, globally diminished deep tendon reflexes, and mild proximal weakness in the shoulder girdle. Sensory modalities were intact. Laboratory investigations, including creatine phosphokinase (CPK) and connective tissue screening, were within normal limits. Nerve conduction studies demonstrated attenuated distal motor responses with marked post-exercise facilitation (>100% amplitude increase), and repetitive nerve stimulation revealed a characteristic increment pattern. Needle EMG showed polyphasic motor units, particularly in the right iliopsoas. The patient had a history of cutaneous melanoma of the neck, resected in 2019.

Discussion: The clinical and neurophysiological findings were consistent with LEMS. While the syndrome is most commonly paraneoplastic and associated with small-cell lung cancer, the patient’s previous melanoma raises the possibility of a rarer neoplastic link to the disease or treatment. Lambert-Eaton syndrome described in a patient treated for metastatic melanoma by the anti-programmed cell death 1 inhibitor, nivolumab,. The presence of autonomic features, such as overactive bladder, further supports the diagnosis of LEMS, which often includes autonomic dysfunction alongside motor symptoms. VG CA channel antibodies are positive.

Conclusion: This case highlights the diagnostic complexity of LEMS and the importance of considering a broad oncologic history, including less common malignancy associations like melanoma. Early recognition through detailed clinical evaluation and electrophysiological testing is essential to initiate appropriate investigations and guide management.