Paraneoplastic cerebellar degeneration (PCD) is a rare neurological disorder characterized by a widespread loss of Purkinje cells associated with a progressive pancerebellar dysfunction. Paraneoplastic syndromes are a group of rare disorders that are triggered by an abnormal immune system response to an underlying (usually undetected) malignant tumor. Patients with paraneoplastic neurological syndrome (PNS) most often present with neurologic symptoms before an underlying tumor is detected.
Paraneoplastic neurologic syndromes include many neurologic disorders including paraneoplastic cerebellar degeneration (PCD) caused by an immune-mediated mechanism other than a metastatic complication in patients with an underlying malignancy. Any part of the nervous system can be involved depending on the type of primary malignancy.