INDIVIDUAL TEST 877
GABA B Receptor Antibodies (IgG)
Indication
Suspicion of paraneoplastic syndromes particularly in autoimmune encephalitis.
Method
Indirect immunofluorescence (IIF) using transfected cells.
Result
The result is reported as positive or negative. A positive result is followed by a titer (serum).
Interpretation
Antibodies against GABA B receptors may occur in classical autoimmune encephalitis. There are relatively few cases published, of which 50% have been women, age when diagnosed between 24-75 years (median 62 years). The antibodies have been associated with small cell lung cancer in 50-60% of the cases. Antibodies may occur together with other autoantibodies in around 50% of the cases (antibodies against GAD-65, VGCC, and TPO).
GABA B receptors belong to the group of extracellular antigens. Generally, immunotherapy is more often effective in autoantibodies directed against extracellular antigens than in autoantibodies against intracellular antigens. Antibody titers can be used to monitor treatment effectiveness. Screening for cancer diagnosis is recommended.
Antibodies against GABA B receptors are graded as Intermediate-risk antibodies with a frequency of >50% of underlying cancer and a positive result yield 2 points PNS score, according to Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes.
References
- Lancaster, Martinez-Hernandez, Dalmau. Encephalitis and antibodies to synaptic and neuronal cell surface proteins. Neurology. 2011 Jul 12;77(2):179-89. PMID: 21747075
- Lancaster, Lai, Peng, et al. Antibodies to the GABA(B) receptor in limbic encephalitis with seizures: case series and characterisation of the antigen. Lancet Neurol 2010;9:67-76. PMID 19962348
- Dalmau J, Geis C, Graus F. Autoantibodies to Synaptic Receptors and Neuronal Cell Surface Proteins in Autoimmune Diseases of the Central Nervous System. Physiol Rev. 2017 Apr;97(2):839-887. PMID: 28298428;
- Graus F, et al. Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. Neurol Neuroimmunol Neuroinflamm. 2021 May 18;8(4):e1014. PMID: 34006622
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ENSKILD ANALYS 877
GABA B receptor-antikroppar (IgG)
Indikation
Misstanke om paraneoplastiska syndrom och framför allt vid autoimmun encefalit.
Metod
Indirekt immunofluorescens (IIF) med transfekterade celler.
Svar
Resultatet anges som positiv eller negativ. Positivt resultat titreras (serum).
Tolkning
Antikroppar mot GABA B receptor kan förekomma vid klassisk autoimmun encephalit. Det finns relativt få fall publicerade varav 50% har varit kvinnor, ålder vid diagnos mellan 24-75 år (median 62 år). Antikropparna har varit associerade med småcellig lungcancer i 50-60% av fallen. Antikropparna kan förekomma tillsammans med andra autoantikroppar i runt 50% av fallen (antikroppar mot GAD-65, VGCC, och TPO).
GABA B receptorerna räknas till gruppen extracellulära antigen. Generellt sett är behandling med immunoterapi oftare effektiv vid autoantikroppar riktade mot extracellulära antigen än vid autoantikroppar mot intracellulära antigen. Antikroppstitrar kan användas för att följa behandlingseffektivitet. Uppföljning med cancerdiagnostik rekommenderas.
Antikropparna riktade mot GABA B bedöms vara Intermediate-risk antibodies med en förekomst på >50% för en underliggande cancer och positivitet ger 2 poäng i PNS score enligt Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes.
Referenser
- Lancaster, Martinez-Hernandez, Dalmau. Encephalitis and antibodies to synaptic and neuronal cell surface proteins. Neurology. 2011 Jul 12;77(2):179-89. PMID: 21747075
- Lancaster, Lai, Peng, et al. Antibodies to the GABA(B) receptor in limbic encephalitis with seizures: case series and characterisation of the antigen. Lancet Neurol 2010;9:67-76. PMID 19962348
- Dalmau J, Geis C, Graus F. Autoantibodies to Synaptic Receptors and Neuronal Cell Surface Proteins in Autoimmune Diseases of the Central Nervous System. Physiol Rev. 2017 Apr;97(2):839-887. PMID: 28298428;
- Graus F, et al. Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. Neurol Neuroimmunol Neuroinflamm. 2021 May 18;8(4):e1014. PMID: 34006622