RESUMO
Stiff-person syndrome (SPS) is an extremely rare disease that is characterised by progressive rigidity and muscle spasms affecting the axial and limb muscles and is difficult to diagnose. In SPS, autoantibodies such as anti-GAD antibody or anti-amphiphysin antibody may be proved, and it is speculated that SPS is GABAergic neurons disorder with the central nervous system due to these antibodies. We report a case of advanced breast cancer with a paraneoplastic SPS. Case: A 52-year-old woman was diagnosed with advanced breast cancer with bilateral multiple lung metastases, bilateral cancerous pleurisy, multiple liver metastases, cancerous peritonitis, and bilateral ovarian metastases. Anti-cancer treatment was not indicated due to poor condition, and oxygenation and pleural drainage and ascites drainage were performed in the palliative care unit. A series of symptoms due to muscle rigidity progressed rapidly which initially manifested as dysphagia, then stiffness of the upper extremities and locomotive disability. So she was diagnosed as paraneoplastic SPS by a neurologist. Despite the partial efficacy of diazepam, it was difficult to increase dosage due to sedation.