A case of paraneoplastic syndrome accompanied by two types of cancer.

A case of paraneoplastic syndrome accompanied by two types of cancer is reported. The patient was a 62 year old man who progressively developed cerebellar ataxia, especially an abnormal gait. The anti-Hu antibody titre was high. A small tumour was detected in the middle lobe of the right lung and was surgically treated. The histology was adenocarcinoma. After lobectomy, however, the ataxia deteriorated, and plasma exchange, 250 ml/kg/day, was conducted for 6 days. After plasma exchange, the anti-Hu antibody titre decreased and the ataxia temporarily ceased to progress. A week after the last plasma exchange, a mass appeared in the anterior cervical region and rapidly increased in size. The biopsy of the neck tumour disclosed a small cell carcinoma. Five months later small cell carcinoma appeared in the left lung. This case shows the importance of searching for small cell carcinoma when anti-Hu antibodies are detected. It is assumed that plasma exchange removed not only a pathogenic factor of ataxia but also a factor which inhibited the growth of the small cell carcinoma. It is recommended that plasmapheresis should be performed with caution in paraneoplastic syndrome when the origin of a tumour is obscure.