Recoverin-antibody-related disease is currently restricted to late-onset ataxia and autoimmune retinopathy, which can be paraneoplastic or not. However, cognitive dysfunction associated with recoverin antibodies has not been reported so far in a homogeneous patient group. Our case series is dedicated to describing the novel phenotype of cognitive impairment associated with recoverin antibodies. We included five patients with cognitive impairment who presented serum recoverin autoantibodies detected by immunoblots in our case series investigation. We also analyzed their psychopathology, clinical data, cerebrospinal fluid (CSF), and neuroimaging data. Five patients with cognitive impairment associated with serum recoverin antibodies exhibited profound dysfunctional learning and verbal memory. In the CSF of 40% of them, we also diagnosed axonal neurodegeneration entailing elevated tau and phosphorylated tau protein levels. Psychopathologies such as affective symptoms (restlessness, depressive mood, anxiety, complaintiveness) and formal thought disorder, such as rumination, were detected in 25-75% of the patients. We hypothesized a role of recoverin autoimmunity in the pineal gland involving consecutive modulation of hippocampus-based memory caused by an altered release of melatonin. We describe a novel phenotype of possible recoverin autoimmunity in patients with cognitive impairment. However, no clear diagnostic clues can be extracted because of the low diagnostic validity of the testing strategies applied. The possibility of recoverin antibody autoimmunity in the pineal gland correlating with a modulation of hippocampus-based memory should be further investigated.

BACKGROUND: Paraneoplastic neurological syndromes (PNS) are rare neurological conditions and they are mostly triggered by autoimmune mechanisms. Cancer-related retinopathies (CAR) are even rarer and commonly related with breast tumor in woman. This limits our knowledge about pathophysiology of CAR. In this study, we question the association between histopathological findings and onconeural antibodies in breast cancer.
METHODS: Thirty-two patients with newly diagnosed breast cancer admitted to the oncology outpatient clinic were included in the study. None of the participants have visual complaints. After the neurological examination of the patients, two tubes of 5 cc venous blood were obtained by screening onconeuronal antibodies. Samples were investigated in ASDETAE (İstanbul University Experimental Medicine Research Institute).
RESULTS: Patients included in the study included one patinet (3.1%) with grade 1, 14 patients (43.8%) with grade 2 and 17 patients (53.1%) with grade 3 invasive breast cancer. Perineural invasion was detected in 5 (15.6%) patients. Progesterone receptor positivity was found in 26 (81.2%) patients and estrogen receptor positivity was found in 27 (84.4%) patients. In 7 (21.9%) patients, CERBB2 was positive and in 25 (78.1%) patients, Ki 67 was positive. A total of 12 (37.5%) patients had onconeuroneal antibody positivity. Antibody positivity was significantly higher in patients with high grade tumor (p=0.008).
CONCLUSIONS: There may be a relationship between tumor grade and the presence of onconeuronal antibodies in breast cancer patients. By the detection of new biochemical markers, significant contribution can be made to the early diagnosis and treatment of underlying cancer.