- Small cell lung cancer (SCLC) is characterized by a relatively high rate of autoimmune phenomena. Paraneoplastic limbic encephalitis (PLE) is an autoimmune syndrome in which a non-neural tumor containing an antigen normally present in the nervous system precipitates an antibody attack on neural tissues. Patients with PLE usually present with rapidly progressive short-term memory deficits, confusion or even dementia. Palmar fasciitis and polyarthritis syndrome (PFPAS) is another autoimmune syndrome characterized by rheumatologic manifestations, especially involving the palms of the hands. We report a case of a 59-year old woman who presented with worsening neurological symptoms of two-week duration, and later coma. The combined clinical, serological, and imaging studies suggested a diagnosis of PLE. A chest computed tomographic scan showed a 1.2 cm-diameter mass in the upper lobe of the left lung that was surgically removed and showed SCLC. Following surgery, neurological symptoms rapidly improved, allowing the patient to receive adjuvant chemotherapy. While in remission for both SCLC and PLE, the patient developed pain, soft-tissue swelling, and stiffness in both palms, suggesting the diagnosis of PFPAS. Five months following the diagnosis of palmar fasciitis, SCLC relapsed with mediastinal and cervical lymphadenopathy. This case report underlines the continuous interaction of SCLC with the immune system, expressed by coexistence of two rare paraneoplastic diseases, PLE, and PFPAS, in a patient with SCLC. While symptoms related to PLE preceded the initial diagnosis of SCLC, other symptoms related to PFPAS preceded relapse.