Paraneoplastic Demyelinating Inflammatory Neuropathy Revealing Metastatic Seminoma: A Case Report

Paraneoplastic neurological syndrome (PNS) is uncommon and not well known. PNS can reveal cancer, but its role in seminomas has not been described explicitly. We report the case of a 36-year-old man with unremarkable medical history and no comorbidities who was diagnosed with a retroperitoneal metastatic seminoma. The patient's general condition deteriorated, and he developed progressive neurological palsy without other clinical anomalies. Electromyography revealed demyelinating, non-lengthy neuropathy. Guillain-Barré syndrome was initially suspected. However, a positron emission tomography scan revealed a retroperitoneal mass, and blood markers revealed increased human chorionic gonadotropin. The patient was diagnosed with PNS, and a computed tomography-guided biopsy revealed a metastatic seminoma without a primary tumor. No circulating neural antibodies were detected. Human polyvalent immunoglobulin was simultaneously administered with chemotherapy. After three cycles of a cisplatin-etoposide-bleomycin, a complete biological and metabolic response rate was observed, and his neurological symptoms rapidly improved. Four years later, the patient responded completely, without any neurological complaints. Paraneoplastic demyelinating inflammatory neuropathy can lead to advanced seminoma diagnosis. Prompt management of seminomas with cisplatin-based regimens provides the best chance of cure for both advanced seminoma and paraneoplastic syndrome.