Effectiveness of Intravenous Cyclophosphamide in a Patient With Anti-amphiphysin Autoimmunity Presenting With Bulbar Palsy and Cerebellar Ataxia: A Case Report.

Anti-amphiphysin antibody is a rare paraneoplastic autoantibody. A case of a 74-year-old man with anti-amphiphysin antibody and multiple symptoms, including bulbar palsy along with cerebellar ataxia, who responded to treatment with intravenous cyclophosphamide is reported. The patient presented with progressive unsteady gait and difficulty in swallowing food and water for three months. On admission, he had severe ataxia, downbeat and horizontal nystagmus, dysarthria, dysphagia, loss of tendon reflexes, and dysuria. Anti-amphiphysin antibodies were detected in the serum, resulting in the diagnosis of non-stiff anti-amphiphysin syndrome. No significant abnormalities were observed in imaging studies of the brain and the whole body. The patient was treated with high-dose intravenous immunoglobulin and steroids, yielding only slight improvement. After two courses of intravenous cyclophosphamide pulse therapy, his neurological symptoms, notably dysphagia and cerebellar ataxia, improved. Follow-up computed tomography and fluorodeoxyglucose-positron emission tomography/computed tomography showed enlarged mediastinal lymph nodes and hypermetabolic uptake of F-18 fluorodeoxyglucose six months after the onset of the neurological symptoms. Histological examination of a lymph node showed metastatic small cell lung cancer. This case highlights the efficacy of cyclophosphamide as second-line immunotherapy for anti-amphiphysin syndrome.