title: Psychotic syndrome associated with anti-Ca/ARHGAP26 and voltage-gated potassium channel antibodies.
abstract: BACKGROUND
  Antibodies to the Rho GTPase-activating protein 26 (ARHGAP26, GRAF1) (also termed anti-Ca) were first described in patients with cerebellar ataxia. However, ARHGAP26 is also expressed in some hippocampal neurons. Moreover, some of the previously reported patients showed cognitive and affective symptoms. It is unknown whether those symptoms reflected involvement of the limbic system or were part of the so-called cerebellar cognitive/affective syndrome.
  
  
  METHODS
  Here, we report a newly diagnosed anti-Ca/ARHGAP26-IgG-positive patient who presented with recurrent psychotic symptoms but no cerebellar ataxia. In addition, low-titer acetylcholine receptor antibodies, voltage-gated potassium channel complex antibodies (but no LGI1 or CASPR2 antibodies) and anti-nuclear antibodies of unknown specificity were detected, suggesting a general autoimmune predisposition. Thymectomy revealed mild thymic nodular hyperplasia.
  
  
  CONCLUSIONS
  This case indicates that the clinical spectrum of ARHGAP26-related autoimmunity might be broader than expected. Studies on the prevalence of anti-Ca/ARHGAP26 in patients with suspected limbic encephalitis seem warranted.
authors: Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Heidelberg, Germany. Electronic address: sven.jarius@med.uni-heidelberg.de.
authors: S
authors: S
authors: Jarius
authors: Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Heidelberg, Germany.
authors: B
authors: B
authors: Wildemann
authors: Euroimmun AG, Lübeck, Germany.
authors: W
authors: W
authors: Stöcker
authors: Department of Neurology, University of Lübeck, Lübeck, Germany.
authors: A
authors: A
authors: Moser
authors: Department of Neurology, University of Lübeck, Lübeck, Germany; Institute of Clinical Chemistry, Neuroimmunology Unit, University Medical Center Schleswig-Holstein Campus Lübeck, Lübeck, Germany. Electronic address: klaus-peter.wandinger@uksh.de.
authors: K P
authors: KP
authors: Wandinger
mesh_terms: D000328:Adult; D000906:Antibodies / Q000378:metabolism*; D014150:Antipsychotic Agents / Q000627:therapeutic use; D002118:Calcium / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D003975:Diazepam / Q000627:therapeutic use; D005260:Female; D020690:GTPase-Activating Proteins / Q000276:immunology*; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007136:Immunoglobulins / Q000627:therapeutic use; D024642:Potassium Channels, Voltage-Gated / Q000276:immunology*; D011618:Psychotic Disorders / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018967:Risperidone / Q000627:therapeutic use
chemical_list: C115971:ARHGAP26 protein, human; D000906:Antibodies; D014150:Antipsychotic Agents; D020690:GTPase-Activating Proteins; D007136:Immunoglobulins; D024642:Potassium Channels, Voltage-Gated; D018967:Risperidone; D003975:Diazepam; D002118:Calcium
keywords: Anti-ARHGAP26; Anti-Ca; Anti-nuclear antibodies; CASPR2; Cerebellar ataxia; GRAF1; GTPase regulator associated with focal adhesion kinase; Kv1.1; Kv1.2; Kv1.7; LGI1; Limbic encephalitis; Oligophrenin 1-like protein; Psychosis; Rho GTPase-activating protein 26; Voltage-gated potassium channels