A Case of Septin-7 Antibody-associated Encephalitis Associated with Seizures and Squamous Cell Lung Carcinoma

ObjectiveTo report a case of septin-7 antibody-associated encephalitis associated with seizures and squamous cell lung carcinoma. BackgroundSeptin-7 IgG is a recently identified autoantibody with fewer than 20 total cases reported in the literature. This autoantibody has been associated with encephalopathy, myelopathy, cerebellar ataxia, and psychiatric changes. Associated malignancy has been reported in a minority of cases, specifically breast adenocarcinoma, non-Hodgkin lymphoma, carcinoid tumor, and myelodysplastic syndrome. To our knowledge, squamous cell lung carcinoma has not been reported in association with septin-7 autoimmunity. Design/MethodsWe present a case of a 77-year-old woman with a history of recurrent left parieto-occipital intraparenchymal hemorrhage secondary to cirrhosis who presented with refractory focal onset seizures. Her seizure semiology consisted of behavioral arrest, yawning, and vomiting. Her seizures were initially attributed to her prior intraparenchymal hemorrhage and lowered seizure threshold from a urinary tract infection. However, her electroencephalography demonstrated bi-temporal epileptiform discharges and her seizures were refractory to multiple anti-epileptic agents. She also developed progressive encephalopathy and new neuropsychiatric symptoms of paranoia and agitation. Additional work-up revealed the presence of a cavitary lung mass. ResultsFurther evaluation revealed positivity for septin-7 IgG at high titers in both serum (1:30720) and cerebrospinal fluid (1:64) at Mayo Clinic Laboratory. A biopsy of the cavitary lung lesion was consistent with squamous cell carcinoma of the lung. High-dose methylprednisolone and intravenous immunoglobulin were initiated with moderate improvement in mental status and seizure frequency. Ultimately, the family decided to transition to hospice, and she passed away five weeks after her diagnosis. ConclusionsThe full clinical and paraneoplastic spectrum of septin-7 IgG-associated central nervous system disorders is not yet fully defined. Our case highlights that presence of septin-7 IgG may be associated with squamous cell lung carcinoma, and seizures may be within the clinical phenotype.