Abstract Introduction Large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive form of non-small cell lung cancer, associated with a poor prognosis. We present a case of immune-mediated paraneoplastic syndrome induced by LCNEC. Case report 70-year-old female with a past medical history of large cell neuroendocrine carcinoma of the lung with metastasis to the brain, presented to the hospital with new complaints of difficulty ambulating, severe right leg pain, neuropathy, and right foot drop. The patient had received her last chemotherapy session two weeks prior to presentation. Computed tomography (CT) of the right hip was negative for acute pathology. Magnetic resonance imaging (MRI) of the cervical, thoracic and lumbar spine, as well as the lumbar plexus with and without contrast were negative for mass, abnormal enhancements, or evidence of neuritis. Neuroforaminal narrowing was seen at L2-L3 and L5-S1. MRI of the brain with and without contrast demonstrated a new right superior cerebellar lesion, while the known frontoparietal mass was stable. Infectious workup, including a lumbar puncture with CSF PCR, cytology and Gram staining, was negative. HIV, syphilis, hepatitis panels, CMV, and EBV testings were negative. Anti-Smith antibody, anti-SS-B, ANA screening, anti-dsDNA, Rheumatoid factor, anti-Hu/Yo antibodies were negative; anti-SS-A was mildly positive at 27. Serum and urine protein electrophoresis were unremarkable. Complement C3 and C4, free kappa and lambda chains, IgA, IgM were unremarkable; IgG was decreased to 576. The patient was started on intravenous methylprednisolone, 1 gram daily, with dramatic improvement of her symptoms-her pain, weakness and foot drop resolved. She completed 5 days of pulse-dose steroids and was transitioned to a prolonged prednisone taper over 4 weeks. Discussion LCNEC account for approximately 1-3% of all lung cancers. While previously documented cases in the literature have reported opsoclonus-myoclonus syndrome and anti-NMDA encephalitis, this case represents an uncommon presentation of paraneoplastic polyneuropathy. The absence of a structural, infectious or rheumatologic cause, with improvement from corticosteroids support an immune-mediated paraneoplastic mechanism. This case highlights the importance of identifying new neurologic symptoms in patients with LCNEC as potentially paraneoplastic phenomena to provide prompt diagnosis and treatment. This abstract is funded by: None
DeLorenzo et al. (Fri,) studied this question.