Encephalomyelitis occurs in paraneoplastic syndrome and acute disseminated encephalomyelitis through different autoimmune mechanisms. No postvaccinal encephalomyelitis other than acute disseminated encephalomyelitis has been reported in patients with malignancy. A 68-year-old woman was admitted because of a headache followed by a gait disturbance and psychomotor retardation 2 days after she had received an influenza vaccination followed by abulia, limb rigidity and hyperreflexia of both legs, and meningeal irritation. Cerebrospinal fluid studies showed increased intracranial pressure, elevated immunoglobulins G and A, and pleocytosis. Contrasted brain magnetic resonance imaging revealed ventriculomegaly and multiple symmetric leptomeningeal enhancement, without demyelinating changes or cortical ribbon signs. Somatosensory evoked potentials and nerve conduction velocity studies suggested myelitis. Encephalomyelitis was diagnosed on the basis of clinical and laboratory examinations. The etiological survey identified a lung adenocarcinoma. Both the encephalomyelitis and the lung adenocarcinoma simultaneously progressed after the vaccination and then, after targeted therapy for lung cancer, simultaneously subsided. In conclusion, postinfluenza-vaccination paraneoplastic encephalomyelitis may occur in patients with lung adenocarcinoma.
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