Chronic inflammatory demyelinating polyneuropathy associated with metastatic malignant melanoma of unknown primary origin.

Paraneoplastic neurological syndromes (PNS) are rare manifestations of malignant disease. It is currently believed that most, if not all, PNS are autoimmune in nature. Proteins expressed on the surface of tumor cells trigger an immune response that cross-reacts with similar proteins in the nervous system, resulting in damage. Moreover, recent studies propose that the appearance of autoimmune phenomena in patients with malignant melanoma implies a strong antitumoral activity and constitutes a marker of improvement in overall survival. We describe a most unusual case of chronic inflammatory demyelinating polyneuropathy (CIDP) occurring in a patient with metastatic malignant melanoma of unknown primary origin who received treatment with interferon alpha-2b. We also review the relevant literature about this infrequent association, discuss on its pathogenesis and underline its importance as surrogate marker, useful to verify the antineoplastic treatment efficacy.