Anti -Iglon5 Syndrome: What we know so far? A non-systematic review

Background: The first report of Anti-IgLON5 syndrome was in 2014. AntiIgLON5 antibodies have a prevalence of 12 in 150,000 patients per year. However, considering the unreported patients, the prevalence can be much higher. Objectives: Provide an overview of the current knowledge of Anti- IgLON5 syndrome. Design and setting: Narrative review. Methods: Non- systematic review on Pubmed database. Results: The IgLON proteins are a family of cell adhesion molecules and the presence of antibodies against IgLON5 is crucial for the AntiIgLON5 Syndrome diagnosis. This syndrome has an expanded clinical spectrum that involves prominent sleep disorder, progressive bulbar dysfunction, gait instability with abnormal eye movements reminiscent, and cognitive deterioration sometimes associated with chorea. The main neuropathological finding is the neuronal loss with hyperphosphorylated tau protein accumulation at the hypothalamus, brainstem tegmentum, hippocampus, periaqueductal gray matter, medulla oblongata, and upper cervical cord. The exact pathogenesis is still unclear and involves a neurodegenerative process and autoimmune response. Early diagnosis is important to avoid unnecessary tests and prevent complications. Important resources for diagnosis are the antibody testing of serum and cerebrospinal fluid for IgLON5-IgG. The Anti-IgLON5 syndrome mortality is high and new studies published described a good response to immune therapy, however, depends on some clinical and analytical characteristics. Conclusions: The Anti-Iglon5 syndrome is a pathology still poorly studied and described in the medical literature (only in case series, for example), being a syndrome probably underdiagnosed. Future studies are needed to thoroughly analyze the aspects of pathogenesis and treatment of this important pathological syndrome.