Genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes

Abstract

Purpose of review We summarize the recent discoveries on genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes (PNS), emphasizing clinical and pathophysiological implications. Recent findings The human leukocyte antigen (HLA) is the most studied genetic factor in autoimmune encephalitis and PNS. The HLA haplotype 8.1, which is widely known to be related to systemic autoimmunity, has been only weakly associated with a few types of autoimmune encephalitis and PNS. However, the strongest and most specific associations have been reported in a subgroup of autoimmune encephalitis that comprises antileucine-rich glioma-inactivated 1 (LGI1) limbic encephalitis, associated with DRB1∗07 : 01, anticontactin-associated protein-like 2 (CASPR2) limbic encephalitis, associated with DRB1∗11 : 01, and anti-IgLON5 disease, associated with DRB1∗10 : 01∼DQA1∗01∼DQB1∗05. Non-HLA genes have been poorly investigated so far in autoimmune encephalitis, mainly in those lacking HLA associations such as anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, with only a few genome-wide association studies (GWAS) reporting equivocal results principally limited by small sample size. Summary Genetic predisposition seems to be driven mostly by HLA in a group of autoimmune encephalitis characterized by being nonparaneoplastic and having predominantly IgG4 autoantibodies. The contribution of non-HLA genes, especially in those diseases lacking known or strong HLA associations, will require large cohorts enabling GWAS to be powerful enough to render meaningful results.

Overview and Diagnostic Approach in Autoimmune Neurology

“…In Olmsted County, Minnesota, the incidence of autoimmune encephalitis increased over time from 0.4/100,000 person-years (1995-2005) to 1.2/100,000 person-years (2006-2015), comparable with the incidence of infectious encephalitis, and African American people were disproportionately affected 5 . Pacific Islander, Māori, or Asian background appears to be a risk factor for NMDA receptor encephalitis, 6 whereas leucine-rich glioma inactivated protein 1 (LGI1) encephalitis is found predominantly in White and Asian individuals 7 . The increase in the incidence of autoimmune encephalitis is attributable to increased detection of people who are antibody positive 5 .…”

“…5 Pacific Islander, Māori, or Asian background appears to be a risk factor for NMDA receptor encephalitis, 6 whereas leucine-rich glioma inactivated protein 1 (LGI1) encephalitis is found predominantly in White and Asian individuals. 7 The increase in the incidence of autoimmune encephalitis is attributable to increased detection of people who are antibody positive. 5 The incidence of paraneoplastic neurologic syndromes in Olmsted County, Minnesota increased over time from 0.4/100,000 person-years (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) to 0.8/100,000 person-years (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)).…”