[Autoimmunity and paraneoplastic neurologic syndromes].

Paraneoplastic syndromes affecting the nervous system are rare and their diagnosis is often difficult when the original cancer is unknown. Recently, high levels of antineuronal antibodies (AB) have been found in serum and CSF of some patients with paraneoplastic syndromes. The anti-Yo AB recognizes 2 proteins of 34 and 62 kd in the cytoplasm of Purkinje cells and in malignant cells of patients suffering from paraneoplastic cerebellar degeneration associated with ovarian and breast cancer. The anti-Hu AB recognizes a 37-40 kd protein in nuclei of neurons and in tumor cells of patients suffering from subacute sensory neuronopathy and encephalomyelitis associated with small cell lung cancer. Other antineuronal AB have been more rarely identified. The presence of high titer of one of these AB in a patient with suspected paraneoplastic syndrome is of great practical interest since it confirms the neurological diagnosis and strongly suggests the location of the primary tumor when the malignancy is unknown. The pathogenetic role of the antineuronal AB is unknown but it is likely that some paraneoplastic syndromes affecting the nervous system are due to an immune reaction against antigens shared by the tumor and the nervous system. To date, no efficient treatment has been found.