[Autoimmunity and cancer: paraneoplastic neurological syndromes associated with small cell cancer]

Paraneoplastic neurological syndromes are mostly associated with small cell lung cancer. Lambert-Eaton myasthenic syndrome appears to be caused by anti-presynaptic calcium channel antibodies. Calcium channels are also present in the cell membrane of small cell lung cancer, which may trigger the formation of anti-calcium channel antibodies. It is the most convincing argument in support of the auto-immune paraneoplastic theory, which refers to cross-antigenicity. Serum of patients with small cell carcinoma and cancer-associated retinopathy contains immunoglobulins against several antigens in the retinal and tumor cells. Patients with chronic intestinal pseudoobstruction (gastrointestinal neuropathy) associated with small cell lung cancer displayed circulating IgG antibodies reactive with neurons of myenteric plexus (anti-enteric neuronal antibodies). On the other hand, high levels of anti-neuronal antibodies (anti-Hu) have been found in the serum and cerebrospinal fluid of patients suffering from subacute encephalomyelitis (limbic encephalitis, cerebellar degeneration, sensory neuronopathy) associated with small cell lung cancer. The pathogenic role of the anti-neuronal antibody is not well established. Nevertheless, the finding of high titer antineuronal antibody in patients with a suggestive clinical syndrome is of great interest since it confirms the paraneoplastic syndrome and suggests the location of the primary tumor when the cancer is unknown.