Paraneoplastic neurodegenerative diseases are defined as damage to central and peripheral nervous tissue related to a malignancy, in the absence of metastases. If they represent first disease manifestation, the diagnosis can pose a real problem. A case of 59-year-old woman is described, who suffered during her last nine months of life from meningoencephalitis, with cranial nerves pareses and progressive quadruparalysis. The CSF exhibited a temporary inflammatory response with slow improvement, whereas the clinical status progressed continually toward terminal bronchopneumonia. An extensive infectious agent search was negative. Though the result of the autoantibody panel available (anti Yo, Hu, Ri) was negative, the paraneoplastic degeneration remained a part of the differential diagnosis. Post-mortem examination revealed residual brain stem meningoencephalitis and advanced cerebellar loss of Purkinje cells, in the presence of a neuroendocrine small cell lung carcinoma in the right lower lobe. The carcinoma only manifested intravitally, with paratracheal lymphadenomegaly on imaging. Rapid progress in the diagnostics of autoimmune neurodegeneration with the increasing spectrum of autoantibody detection tools has recently increased the possibilities of revealing clinically silent, primary manifesting neurodegeneration. In the future, it may also represent a target for therapeutic intervention.

        Key words: paraneoplastic encephalitis, small cell lung carcinoma, paraneoplasia, latent malignancy.