P/Q and N-type Voltage-gated Calcium Channel Binding Antibodies Associated with Paraneoplastic Chorea and Mixed Invasive Ductal and Lobular Carcinoma of the Breasts in an Elderly Patient

Abstract

Paraneoplastic neurologic syndromes are a group of immune-mediated, cancer-associated disorders affecting the nervous system. While these syndromes are not understood fully, they are reportedly caused by an immune response against common antigens expressed by the cancer and nervous system. We describe the course of a patient who suffered paraneoplastic chorea before being diagnosed with breast cancer. A 70-year-old female presented with complaints of "shaking" movements of her head. History, physical exam findings, and preliminary workup ruled out the hereditary, metabolic, and infectious causes of chorea while brain computed tomography (CT) ruled out chorea due to a basal ganglia lesion. A paraneoplastic antibody panel identified N-type and P/Q-type voltage-gated (V-G) calcium channel binding antibodies. Subsequent age-appropriate cancer screening, which included a colonoscopy and screening mammograms, identified breast cancer. The patient had bilateral total mastectomies. Histopathology confirmed mixed invasive ductal and lobular carcinoma that was estrogen receptor positive, progesterone receptor positive, and human epidermal growth factor receptor 2 negative. In addition to mastectomies, the patient received adjuvant anastrozole. The appearance of choreiform movements before the diagnosis of breast cancer and the presence of paraneoplastic antibodies indicated that the chorea was most likely paraneoplastic in nature. Our patient continues to have choreiform movements despite undergoing bilateral mastectomies and receiving anastrozole, prednisone, and rituximab. We suspect the mastectomies and immune modulating therapies have not had an effect on her chorea because her P/Q and N-type V-G calcium channel binding antibodies may be intracellular. This case of paraneoplastic chorea associated with breast cancer is unusual. To the best of our knowledge, only one other case of paraneoplastic chorea associated with breast cancer has been reported in the English literature.