RT Journal Article SR Electronic T1 Three Paraneoplastic Syndromes preceding an Occult Breast Cancer (688) JF Neurology JO Neurology FD Lippincott Williams & Wilkins SP 688 VO 94 IS 15 Supplement A1 Ibrikji, Sidonie A1 El Halabi, Tarek A1 Sawaya, Raja A1 Atweh, Samir YR 2020 UL http://n.neurology.org/content/94/15_Supplement/688.abstract AB Objective: We describe the case of a 49 year-old lady, diagnosed with amphiphysin-induced stiff person syndrome (SPS), resistant to multiple lines of symptomatic and immunologic treatments. An initial screen for malignancy, including breast cancer, was negative. She also developed asymptomatic cervical transverse myelitis and central diabetes insipidus (DI), the latter resolving with IVIG treatment.The combination of those 3 entities elicited a more meticulous search for malignancy. A new left axillary lymph node was found on physical exam, and its sampling revealed metastatic ductal carcinoma (grade 3/3); ultimately diagnosing the patient with breast cancer preceded by the onset of possibly three paraneoplastic syndromes.Background: Stiff person syndrome (SPS) is a rare disorder characterized by rigidity, painful spasms and psychiatric manifestations, and caused by autoantibodies that inhibit inhibitory neurons. Amphiphysin is a synaptic protein responsible for endocytosis of the vesicle membrane after release of GABA (Gamma-Aminobutyric Acid) from the axonal ends, against which antibodies cause the paraneoplastic variant of SPS, mainly associated with breast cancer. The coexistence of transverse myelitis and SPS has been rarely reported, but amphiphysin antibodies are believed to target spinal epitopes and induce toxic lesions in the spinal cord. Furthermore, patients who develop central diabetes insipidus (DI) secondary to a neoplasm usually have a pituitary metastasis. Rare are the cases where DI is considered paraneoplastic with an intact pituitary on imaging.Design/Methods: Not applicableResults: Not applicableConclusions: This is the first reported case of ductal carcinoma of the breast preceded by amphiphysin-related SPS, transverse myelitis and central DI, considered as 3 paraneoplastic entities.Disclosure: Dr. Ibrikji has nothing to disclose. Dr. El Halabi has nothing to disclose. Dr. Sawaya has nothing to disclose. Dr. Atweh has nothing to disclose.