Influenza-Triggered Seronegative Myasthenia Gravis in an ALK-Positive Lung Cancer Patient on Chronic Alectinib: A Case Report

A 51-year-old man with anaplastic lymphoma kinase-positive non-small-cell lung cancer on long-term alectinib presented with fever, cough, and progressive generalized weakness. He tested positive for influenza A and rapidly developed respiratory failure requiring intubation. Neurological examination demonstrated ptosis, oculobulbar involvement, and proximal weakness. Repetitive nerve stimulation showed a decremental response, while assays for acetylcholine receptor, anti-muscle-specific-kinase, and anti-lipoprotein receptor-related protein 4 antibodies were negative. A diagnosis of seronegative myasthenia gravis was established. The patient received intravenous immunoglobulin, plasma exchange, pyridostigmine, corticosteroids, and azathioprine with gradual clinical improvement. Reports of neuromuscular complications related to anaplastic lymphoma kinase inhibition remain limited, underscoring the importance of vigilance in oncologic patients presenting with respiratory failure. Early recognition of myasthenia gravis in this population is critical to initiate appropriate immunotherapy and supportive management. This case illustrates the difficulty of distinguishing underlying disease and treatment-related effects from new-onset neurological syndromes. It highlights the importance of neurological considerations in cases of progressive respiratory difficulty and posits a putative link between chronic immunosuppression and subsequent susceptibility to autoimmune insult, as well as the need for more aggressive treatment in the setting of immunosuppression.