Prevalence of serum anti-neuronal autoantibodies in patients admitted to acute psychiatric care.
Autoimmune encephalitis associated with anti-neuronal antibodies may be challenging to distinguish from primary psychiatric disorders. The significance of anti-neuronal antibodies in psychiatric patients without clear evidence of autoimmune encephalitis is unknown. We investigated the serum prevalence of six anti-neuronal autoantibodies in a cohort of unselected patients admitted to acute psychiatric care.



Serum was drawn from 925 patients admitted to acute psychiatric in-patient care. Psychiatric diagnoses were set according to International Classification of Diseases (ICD)-10 criteria. Antibody analysis was performed with an indirect immunofluorescence test for N-methyl d-aspartate receptor (NMDAR) antibodies and five other anti-neuronal autoantibodies of the immunoglobulin (Ig) classes IgA, IgG and IgM isotype.



Anti-neuronal autoantibodies were found in 11.6% of patients: NMDAR antibodies in 7.6%, contactin-associated protein-like 2 (CASPR2) antibodies in 2.5%, glutamic acid decarboxylase-65 (GAD65) antibodies in 1.9%, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antibodies in 0.1%. Leucine-rich glioma-inactivated protein-1 (LGI1) and γ-aminobutyric acid B (GABAB) receptor antibodies were not detected. NMDAR antibodies of class IgG were present in five patients only (0.5%). NMDAR antibodies of all Ig classes were equally prevalent in patients with and without psychosis. There were no significant differences in antibody prevalence in the different diagnostic categories, except for a higher odds ratio of being NMDAR antibody positive for patients without a specific psychiatric diagnosis.



NMDAR IgG autoantibodies, which are known to be strongly associated with anti-NMDAR encephalitis, were rarely found. CASPR2 and GAD65 antibodies were more frequently encountered in the present study than previously reported. Further research on the clinical significance of anti-neuronal autoantibodies in patients with acute psychiatric symptoms is needed.
Department of Neuroscience,Norwegian University of Science and Technology,Trondheim,Norway.
M
M
Schou
Department of Neuroscience,Norwegian University of Science and Technology,Trondheim,Norway.
S G
SG
Sæther
Institute for Experimental Immunology,Euroimmun AG,Lübeck,Germany.
K
K
Borowski
Institute for Experimental Immunology,Euroimmun AG,Lübeck,Germany.
B
B
Teegen
Department of Neuroscience,Norwegian University of Science and Technology,Trondheim,Norway.
D
D
Kondziella
Institute for Experimental Immunology,Euroimmun AG,Lübeck,Germany.
W
W
Stoecker
Department of Neuroscience,Norwegian University of Science and Technology,Trondheim,Norway.
A
A
Vaaler
Department of Neuroscience,Norwegian University of Science and Technology,Trondheim,Norway.
S K
SK
Reitan
D000328:Adult; D001323:Autoantibodies / Q000276:immunology*; D001714:Bipolar Disorder / Q000276:immunology; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000276:immunology; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology; D006760:Hospitalization; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins / Q000276:immunology; D001523:Mental Disorders / Q000276:immunology*; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000276:immunology; D009664:Norway; D011506:Proteins / Q000276:immunology; D011618:Psychotic Disorders / Q000276:immunology; D018091:Receptors, AMPA / Q000276:immunology; D018080:Receptors, GABA-B / Q000276:immunology; D016194:Receptors, N-Methyl-D-Aspartate / Q000276:immunology; D012559:Schizophrenia / Q000276:immunology
D001323:Autoantibodies; C403049:CNTNAP2 protein, human; D047908:Intracellular Signaling Peptides and Proteins; C116499:LGI1 protein, human; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D018091:Receptors, AMPA; D018080:Receptors, GABA-B; D016194:Receptors, N-Methyl-D-Aspartate; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2

               N-methyl D-aspartate (NMDA) receptor; Antibodies; autoimmunity; psychiatry