Background: Paraneoplastic neurological syndromes are rare conditions manifest as psychiatric/neurological symptoms. They are caused by autoimmunne cross-reaction leading to destruction of the central nervous system.
Case: We present the case of a 64-year-old patient hospitalized for 6 months at the Department of Psychiatry for persisting depression. During that time he progressed to delirium. A diagnosis of diffuse encephalopathy was made, but further examination revealed a small cell lung cancer with generalisation. A paraneoplastic syndrome was finally diagnosed after autoptic and histologic examination.
Conclusion: Paraneoplastic neurological syndromes can be early signs of malignancy and may considerably precede oncologic diagnosis.