Anti-Hu--associated paraneoplastic encephalomyelitis/sensory neuronopathy. A clinical study of 71 patients.

We studied 71 patients with "paraneoplastic" encephalomyelitis, sensory neuronopathy, or both associated with the presence of the anti-Hu antibody in their serum. Most (78%) had small-cell lung cancer. In 9 patients no tumor was detected. Fifty-two patients (73%) had signs and symptoms of multifocal involvement of the nervous system; in 28 (39%), 2 areas, and in 24 (34%), 3 or more areas were clinically affected. Sensory neuronopathy was present in 52 patients (74%), but in only 44 (62%) did it dominate the course of the disease. Other predominant findings were: motor neuron dysfunction (14 patients, 20%), limbic encephalopathy (14, 20%), cerebellar symptoms (11, 15%), brainstem encephalopathy (10, 14%), and autonomic nervous system dysfunction (7, 10%). The presence of the anti-Hu antibody prompted a search for the tumor in 60% of the patients; the tumor when found was usually small and remained localized until death, or was demonstrated only at autopsy. Treatment using steroids and plasmapheresis, immunosuppressants, or both, did not improve the paraneoplastic symptoms. Autonomic and respiratory failure, either of central origin or secondary to neuromuscular weakness, were the principal causes of death. Patients with rapidly developing sensory neuropathy or symptoms of encephalomyelitis should be studied for the presence of the anti-Hu antibody; if the antibody is found, the possibility of small-cell lung cancer should be investigated. If a tumor is not found in the initial search, one may become evident in several months.