Lymbic encephalitis and demyelinating sensory neuropathy in a PT with oats cell carcinoma, anti-HU and anti-gad antibodies

We describe a 46-old-man who developed subacute anxiety, confusional state with hallucination, gait ataxia, asymmetrical sensory neuropathy associated with oats cell lung carcinoma, and high titer anti-Hu antibodies in both serum and CSF. Neurophysiological studies revealed a severe demyelinating neuropathy involving preferentially sensory fibers. Clinically the patient was bed ridden. CSF revealed a clear alteration of the blood-brain barrier with increased CSF proteins (300 mg/dl). After two cycles of chemotherapy, total CT scan became negative and after 18-month follow-up was still negative. After five cycles of high dose I.V. Ig the patient was able to walk with bilateral supports. Hu antibodies became negative in serum and were markedly decreased in CSF. Mild rigidity with painful spasm in the trunk associated with diabetes mellitus was present. An immunoprecipitation assay of GAD 35 S-methionine-labeled showed the presence of anti-GAD antibodies (9.7 UI) (cut off>3 UI). Western blot analysis detected immunoreactivity only against the 67-kDa GAD subunit. Our patient is an example of antigen-driven immune response induced by carcinoma.