RT Journal Article SR Electronic T1 A rare case of long-term paraesthesia diagnosed as a paraneoplastic syndrome by anti-SOX1 antibody determination JF BMJ Case Reports JO BMJ Case Reports FD BMJ Publishing Group Ltd SP e228916 DO 10.1136/bcr-2018-228916 VO 12 IS 7 A1 Oriol Mirallas A1 Nuria Rial A1 Berta Martín-Cullell A1 Jesus Recio-Iglesias YR 2019 UL http://casereports.bmj.com/content/12/7/e228916.abstract AB Paraneoplastic syndromes (PS) are a rare presentation of cancer, most commonly associated with small cell lung cancer (SCLC), breast cancer and haematologic malignancies. The diagnosis of PS is challenging because it could affect multiple organ systems and it may present before the tumour is visible by imaging. We report a malignant tumour diagnosed in a male patient who referred long-term paraesthesia and proximal muscle strength loss. After ruling out common causes of polyneuropathy, the anti-SOX1 antibody gave light to the diagnosis. A pulmonary opacity in the upper right lobe was observed in the chest X-ray and a pulmonary tumour was later confirmed by CT scan. The biopsy of the cervical lymphadenopathy determined an SCLC, which caused a PS called Lambert-Eaton myasthenic syndrome (LEMS). Our case raises awareness of a rare PS presentation, which can be diagnosed by specific antibodies, allowing early diagnosis and treatment of lung cancer.