Chronic Intestinal Pseudo-obstruction and Orthostatic Hypotension Associated with Small Cell Lung Cancer that Improved with Tumor Reduction after Chemoradiotherapy.

Chronic intestinal pseudo-obstruction (CIPO) is a rare disease with symptoms of ileus without obstruction. Most cases of CIPO are idiopathic, and CIPO as a paraneoplastic neurological syndrome (PNS) associated with small cell lung cancer (SCLC) is rare. A 63-year-old man was diagnosed with functional ileus and confined to bed due to orthostatic hypotension. Chest computed tomography revealed a right hilar mass suspected of being lung cancer. Based on detailed examinations, he was diagnosed with limited-stage SCLC. His symptoms were confirmed as PNS because his serum anti-Hu antibody was positive. His PNS was improved with complete tumor reduction by chemoradiotherapy.