A Rare Case of Lambert-Eaton Myasthenia Syndrome With Dysphasia and Dysarthria

Lambert-Eaton Myasthenic Syndrome (LEMS) is a rare autoimmune disorder resulting in muscle weakness. LEMS typically presents with progressive proximal muscle weakness, especially in the lower extremities, areflexia, and autonomic dysfunction. Bulbar involvement and respiratory compromise tend to occur later in the disease course and usually in severe, advanced cases. We report a unique case of a 50-year-old male with a known history of LEMS, autoimmune retinopathy, erectile dysfunction, and prediabetes who presented with progressive bulbar symptoms - slurred speech and difficulty swallowing - without accompanying weakness in the upper or lower extremities. Despite receiving four doses of intravenous immunoglobulin (IVIG) prior to admission with no improvement, he showed a significant clinical response to six sessions of plasmapheresis. Notably, the absence of limb weakness and preserved motor strength throughout his hospital stay raised diagnostic uncertainty, prompting evaluation for myasthenia gravis, which was ruled out through negative acetylcholine receptor antibody testing and reaffirmed voltage-gated calcium channel (VGCC) antibody positivity. Chest imaging showed no underlying malignancy. This case illustrates an atypical LEMS presentation dominated by severe bulbar dysfunction in the absence of limb involvement or respiratory failure, which is uncommon and may mimic other neuromuscular junction disorders such as myasthenia gravis. The favorable response to plasmapheresis emphasizes the importance of early recognition and aggressive immunomodulatory treatment in preventing clinical deterioration. Clinicians should maintain a high index of suspicion for LEMS even in unusual presentations to ensure timely and appropriate management.