Vial

INDIVIDUAL TEST 831

VGKC (voltage gated potassium channel) antibodies

Indication Suspicion of autoimmune encephalitis and paraneoplastic symptoms. 

Method Radioimmunoprecipitation (RIA). 

Result The result is reported as negative or positive with a value (pmol/L). 

Interpretation Autoantibodies against potassium channel complex are primarily seen in patients with neuromyotonia, Morvan's syndrome, autoimmune encephalitis or idiopathic epilepsy. These antibodies are often directed to the potassium channel - associated proteins Caspr2 (contactin -associated protein -2) and LGI1 (leucine -rich, glioma inactivated protein 1) and in very rare cases to Contactin 2. Antibodies against Caspr2 are more commonly seen in neuromyotonia and Morvan's syndrome, while antibodies against LGI1 are more commonly seen in autoimmune encephaliti. Antibodies against VGKC has been reported to be associated with cancer in approximately 30% of cases with neuromyotonia and 40% of Morvan's syndrome cases. Thymoma is the most common. Tumours are very rare in patients who has VGKC antibodies and associated autoimmune encephalitis or idiopathic epilepsy. 

More samples are reported positive in the analysis of antibodies against VGKC than in the analysis of antibodies against CASPR2 and LGI1. This is because more antigens are part of the VGKC-complex. Compared to a healthy normal material, the analysis has 98% specificity. In the analysis of serum from patients with symptoms suspected to be associated with VGKC antibodies, sensitivity has been shown to be approximately 90%. The relevance of autoantibodies with levels below 300 pmol/L is uncertain. In autoimmune encephalitis, the antibodies level is often over 300-500 pmol/L. 

VGKC is an extracellular antigen. Generally, treatment with immunotherapy is more effective with autoantibodies directed against extracellular antigens than with autoantibodies against intracellular antigens. 

References 
  • Harrower T. et al. (2006). A case of voltage-gated potassium channel antibody-related limbic encephalitis. Nature 2:6:339-343. PMID: 16932578. 
  • Irani S. et al. (2010).Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvans syndrome and acquired neuromyotonia. Brain. 2010 Sep;133(9):2734-2748. PMID: 20663977. 
  • Olberg H. et. al. Neurological manifestations related to level of voltage-gated potassium channel antibodies. J Neurol Neurosurg Psychiatry. 2013 Aug;84(8):941-943. PMID: 23595945. 
  • 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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Vial

ENSKILD ANALYS 831

VGKC (Kaliumkanal-komplex) antikroppar

Indikation Misstanke om autoimmun encefalit och paraneoplastiska symptom. 

Metod Radioimmunoprecipitation (RIA). 

Svar Resultatet anges som negativt eller positivt. Positivt resultat följs åt med koncentration (pmol/L). 

Tolkning Autoantikroppar riktade mot VGKC ses framför allt hos patienter med neuromyotoni, Morvans syndrom, autoimmun encefalit eller idiopatisk epilepsi. Dessa antikroppar är ofta riktade mot de kaliumkanal-associerade proteinerna CASPR2 (contactin- associated protein-2) och LGI1 (leucine-rich, glioma inactivated protein 1) samt i mycket ovanliga fall mot Contactin-2.  

Antikroppar mot CASPR2 ses oftare vid neuromyotoni och Morvans syndrom, medan antikroppar mot LGI1 oftare ses vid autoimmun encefalit. Antikroppar mot VGKC har rapporterats vara associerade med cancer i ca 30% av fallen med neuromyotoni och 40% av fallen med Morvans syndrom. Tymom är vanligast. Tumörer är mycket ovanliga hos patienter som har VGKC antikroppar och associerad autoimmun encefalit eller idiopatisk epilepsi. 

Fler prover blir positiva vid analys av antikroppar mot VGKC än vid analys av antikroppar mot CASPR2 och LGI1. Detta beror på att fler antigen ingår i VGKC-komplexet. Jämfört med ett friskt normalmaterial har analysen 98% specificitet. Vid analys av serum från patienter med symtom som misstänks vara associerade med antikroppar mot VGKC har sensitiviteten visats vara ungefär 90%. Relevansen av autoantikroppar med nivåer under 300 pmol/L är tveksam. Vid autoimmun encefalit är antikroppsnivån ofta över 300-500 pmol/L. 

VGKC räknas till ett extracellulärt antigen. Generellt sett är behandling med immunoterapi oftare effektfull vid autoantikroppar riktade mot extracellulära antigen än vid autoantikroppar mot intracellulära antigen. 

Referenser 
  • Harrower T. et al. (2006). A case of voltage-gated potassium channel antibody-related limbic encephalitis. Nature 2:6:339-343. PMID: 16932578. 
  • Irani S. et al. (2010).Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvans syndrome and acquired neuromyotonia. Brain. 2010 Sep;133(9):2734-2748. PMID: 20663977. 
  • Olberg H. et. al. Neurological manifestations related to level of voltage-gated potassium channel antibodies. J Neurol Neurosurg Psychiatry. 2013 Aug;84(8):941-943. PMID: 23595945. 
  • 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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