Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Paraneoplastic cerebellar degeneration ?
    ### Response:
    Paraneoplastic syndromes are a group of rare disorders that include paraneoplastic cerebellar degeneration (PCD). Paraneoplastic syndromes are thought to result from an abnormal immune response to an underlying (and often undetected) malignant tumor. PCD is a rare, non-metastatic complication of cancer.
    