Anti-VGKC-complex encephalitis

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Anti-VGKC-complex encephalitis
Specialty Neurology

Anti-VGKC-complex encephalitis are caused by antibodies against the voltage gated potassium channel-complex (VGKC-complex) and are implicated in several autoimmune conditions including limbic encephalitis, epilepsy and neuromyotonia (i.e. Isaacs' Syndrome). [1]

Contents

Research into autoimmune encephalitides have significantly advanced recently. Both tumour associated (paraneoplastic) and nonparaneoplastic conditions are recognized. Different antibodies are more or less selective for different parts of the brain. Antibodies target intracellular antigens in classic paraneoplastic syndromes, but synaptic proteins in nonparaneoplastic conditions. VGKC-complex autoimmune encephalitis is an example of the latter form.

Antibodies directed against VGKC were first reported in neuromyotonia. [2] Further studies led to VGKC antibodies being recognized in Morvan’s syndrome and limbic encephalitis as well. [3] It was for many years erroneously presumed that antibodies detected in a VGKC assay were targeted against the channel itself. But the heterogeneous presentation of patients was difficult to explain. The original assays for the detection of VGKC antibodies used Iodine-125 labelled dendrotoxin and the relatively mild detergent 2% digitonin on mammalian brain homogenate, and VGKC with complexed proteins was extracted. [2] Co-precipitated proteins would thus also be detected in this assay. It’s now acknowledged that most VGKC antibodies are instead directed towards associated/complexed proteins. In a particular study of 96 patients with VGKC antibodies detected with the radioimmunoprecipitation assay, only 3 (3%) had antibodies towards the Kv1 subunit of the VGKC channel, 55 (57%) had antibodies against Leucine-rich, glioma Inactivated 1 (LGI1), 19 had antibodies reacting with Contactin-associated protein 2 (CASPR 2), 5 had antibodies against Contactin-2 and 18 (19%) had antibodies with unknown specificity. [4] Of the patients with Contactin-2 antibodies, 4/5 had antibodies against other antigens as well.

Signs and symptoms

Signs and symptoms depend on the targeted antigen, but the features in patients with different antibodies often overlap. The most characteristic feature found in a case series was cognitive impairment and seizures in anti-LGI-1 positive patients, and peripheral motor hyperexcitability in anti-CASPR2 positive patients. [5]

anti-LGI-1 encephalitis: Patients with anti-LGI1 encephalitis have limbic encephalitis with amnesia and/or confusion (100%) and seizures (84-92 %) [4] [6] Other reported features include hyponatremia (in 60%), movement disorders (myoclonus/dyskinesia), sleep disorders (hypersomnia, insomnia, REM sleep behavior disorder, sleep reversal) and ataxia. Tonic seizures, with movements of the leg, arm or face, refractory to treatment with anti-epileptic drugs may precede the disorders, and should lead to testing for anti-LGI1 antibodies. [7]

Anti-CASPR2 nervous system manifestations: Patients with anti-CASPIR2 antibodies develop symptoms from the CNS and/or the peripheral nervous system. [8] The classic presentation is with Morvan’s syndrome, a disease with the features of neuromyotonia (i.e. peripheral hyperexcitability) and limbic encephalitis. Other patients present with isolated neuromyotonia or limbic encephalitis.[ citation needed ]Patients with anti-DPPX encephalitis present with symptoms of hyperexcitability such as agitation, tremor, muscle rigidity and gastrointestinal symptoms. [8]

Causes

The causes are in general unknown. However, a permeable intestine caused by microbiome dysbiosis has been implicated. The exposure to modern-day gluten proteins also causes the release of zonulin. Zonulin regulates intestinal lining tight junctions. HLA-DQ2 and HLA-DQ8 gene-carriers are also more prone. A paper published by Finn E. Somnier 15 April 2015 shows co-currence of autoantibodies. Some of the patients have tumours. The number of patients with anti-LGI1 antibodies and tumours have been reported to be between 0 and 11% in anti-LGI-1 antibody positive patients, and between 0-30 % in anti-CASPR2 antibody positive patients. [4] [6] Tumours have not been reported in patients with anti-DPPX antibodies. [8] The associated tumour is often a thymoma. [8]

Pathophysiology

Patients with autoimmune encephalitis have antibodies towards synaptic proteins with neuronal functions. The antibodies are presumed to be disease causing, just like the acetylcholine receptor antibodies in myasthenia gravis.[ citation needed ]

The voltage-gated potassium channel (VGKC), like other ion channels, belong to a multiprotein complex. Some of the proteins which associates to the channel directly/indirectly include, but are not limited to, LGI1, CASPR2, Contactin2, DPPX, ADAM22 and ADAM23. LGI1 is a secreted neuronal protein which binds to ADAM22 and ADAM23 and thus crosslinks pre-synaptic VGKC with post-synaptic AMPA receptor. An inherited form of human epilepsy known as autosomal dominant partial epilepsy with auditory features (ADPEAF) has been found to be caused by mutations of the LGI1 gene. LGI1 knockout mice cause lethal epilepsy and the heterozygous mice have a lowered seizure threshold. [9] Mutations of CNTNAP2 (the gene encoding CASPR2) have been reported to be associated with intellectual disability, motor impairment and epilepsy. [10]

Diagnosis

The diagnosis of autoimmune encephalitis is based on the exclusion of differential diagnosis. The first step is a clinical evaluation. Biochemical tests may reveal hyponatremia and the other features of SIADH. [11] Relevant supplementary tests are listed in table 1. [12] The diagnosis of VGKC-complex associated limbic encephalitis should be suspected in both men and women presenting with subacute debut of disorientation, confusion and amnesia especially when associated with seizures and signal change of the medial temporal lobe on MRI.[ citation needed ]

Investigation methodsComments
MRI Exclusion of differential diagnosis (e.g. cerebrovascular disease). Hyperintensity of affected regions on T2-images is characteristic. Sensitivity 60-84 %. [4] [6]
EEG Exclusion of differential diagnosis. Non-characteristic findings may be found in autoimmune encephalitis.
Lumbar puncture Exclusion of differential diagnosis (e.g. infectious diseases). Abnormalities may be found in autoimmune encephalitis.
Immunofluorescence/immunohistochemistry On mammalian brain.
Rodent hippocampal culture
Cell based assaysUsing cell lines (e.g. HEK 293) transfected with recombinant proteins. Commercial products exists.
Radioimmunoassay Non specific. Have the ability to detect antibodies towards undescribed VGKC-complex associated antigens. The complex probably contains unidentified antigens since about 20% of patients have antibodies which can’t be detected with the more specific assays.

Treatment

The treatment is largely based on the treatment of anti-NMDAR encephalitis which is the most common autoimmune encephalitis. Treatment of an associated tumour is implicated in all paraneoplastic neurologic syndromes. Case series have been published where treatment has consisted of combinations of IVIG, plasmapheresis, glucocorticoids/other immunosuppressant drugs and rituximab.[ citation needed ]

Prognosis

The prognosis with treatment is generally good and much better than in the classic paraneoplastic syndromes. In one of the two biggest case series, patients with anti-CASPR2 antibodies without tumours improved on average from a Modified Rankin Score (MRS) of 4 (moderate severe disability) to an MRS of 1 (no significant disability despite symptoms). [4] However, patients with both anti-CASPR2 antibodies and tumours often deteriorated despite treatment. The improvements seen in patients with anti-LGI1 antibodies were slightly better.[ citation needed ]

Epidemiology

The mean incidence of anti-LGI1 in Denmark is 1,1 per million compared to 3,3 per million for anti-NMDAR antibodies (NR1). [13] The disorders may be underdiagnosed due to the lack of knowledge about the conditions and the limited availability of diagnostic tests. The group of patients with anti-LGI1 antibody associated limbic encephalitis have a male predominance and a mean age of about 60 years (variation 30–80 years). [6] The other disorders with associated antibodies also seem to affect mostly older men.[ citation needed ]

See also

Related Research Articles

Angela Vincent is Emeritus professor at the University of Oxford and a Fellow of Somerville College, Oxford.

<span class="mw-page-title-main">Lambert–Eaton myasthenic syndrome</span> Medical condition

Lambert–Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder characterized by muscle weakness of the limbs.

Neuromyotonia (NMT) is a form of peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potentials of peripheral origin. NMT along with Morvan's syndrome are the most severe types in the Peripheral Nerve Hyperexciteability spectrum. Example of two more common and less severe syndromes in the spectrum are Cramp Fasciculation Syndrome and Benign Fasciculation Syndrome. NMT can have both hereditary and acquired forms. The prevalence of NMT is unknown.

Morvan's syndrome is a rare, life-threatening autoimmune disease named after the nineteenth century French physician Augustin Marie Morvan. "La chorée fibrillaire" was first coined by Morvan in 1890 when describing patients with multiple, irregular contractions of the long muscles, cramping, weakness, pruritus, hyperhidrosis, insomnia and delirium. It normally presents with a slow insidious onset over months to years. Approximately 90% of cases spontaneously go into remission, while the other 10% of cases lead to death.

<span class="mw-page-title-main">Neuromuscular junction</span> Junction between the axon of a motor neuron and a muscle fiber

A neuromuscular junction is a chemical synapse between a motor neuron and a muscle fiber.

<span class="mw-page-title-main">Stiff-person syndrome</span> Human medical condition

Stiff-person syndrome (SPS), also known as stiff-man syndrome, is a rare neurologic disorder of unclear cause characterized by progressive muscular rigidity and stiffness. The stiffness primarily affects the truncal muscles and is superimposed by spasms, resulting in postural deformities. Chronic pain, impaired mobility, and lumbar hyperlordosis are common symptoms.

Paraneoplastic cerebellar degeneration (PCD) is a paraneoplastic syndrome associated with a broad variety of tumors including lung cancer, ovarian cancer, breast cancer, Hodgkin’s lymphoma and others. PCD is a rare condition that occurs in less than 1% of cancer patients.

Generalized epilepsy with febrile seizures plus (GEFS+) is a syndromic autosomal dominant disorder where affected individuals can exhibit numerous epilepsy phenotypes. GEFS+ can persist beyond early childhood. GEFS+ is also now believed to encompass three other epilepsy disorders: severe myoclonic epilepsy of infancy (SMEI), which is also known as Dravet's syndrome, borderline SMEI (SMEB), and intractable epilepsy of childhood (IEC). There are at least six types of GEFS+, delineated by their causative gene. Known causative gene mutations are in the sodium channel α subunit genes SCN1A, an associated β subunit SCN1B, and in a GABAA receptor γ subunit gene, in GABRG2 and there is another gene related with calcium channel the PCDH19 which is also known as Epilepsy Female with Mental Retardation. Penetrance for this disorder is estimated at 60%.

<span class="mw-page-title-main">Hashimoto's encephalopathy</span> Human disease (neurological condition)

Hashimoto's encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a neurological condition characterized by encephalopathy, thyroid autoimmunity, and good clinical response to corticosteroids. It is associated with Hashimoto's thyroiditis, and was first described in 1966. It is sometimes referred to as a neuroendocrine disorder, although the condition's relationship to the endocrine system is widely disputed. It is recognized as a rare disease by the NIH Genetic and Rare Diseases Information Center.

<span class="mw-page-title-main">Limbic encephalitis</span> Inflammation involving the limbic system in the brain

Limbic encephalitis is a form of encephalitis, a disease characterized by inflammation of the brain. Limbic encephalitis is caused by autoimmunity: an abnormal state where the body produces antibodies against itself. Some cases are associated with cancer and some are not. Although the disease is known as "limbic" encephalitis, it is seldom limited to the limbic system and post-mortem studies usually show involvement of other parts of the brain. The disease was first described by Brierley and others in 1960 as a series of three cases. The link to cancer was first noted in 1968 and confirmed by later investigators.

A paraneoplastic syndrome is a syndrome that is the consequence of a tumor in the body. It is specifically due to the production of chemical signaling molecules by tumor cells or by an immune response against the tumor. Unlike a mass effect, it is not due to the local presence of cancer cells.

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<span class="mw-page-title-main">LGI1</span> Protein-coding gene in the species Homo sapiens

Leucine-rich, glioma inactivated 1, also known as LGI1, is a protein which in humans is encoded by the LGI1 gene. It may be a metastasis suppressor.

Neuromuscular junction disease is a medical condition where the normal conduction through the neuromuscular junction fails to function correctly.

Ian Kirkland Hart FRCP was a lecturer and consultant in neurology at the Walton Centre in Liverpool. He ran a clinic for neurological paraneoplastic syndromes, myasthenia gravis, neuromyotonia, Lambert–Eaton myasthenic syndrome and autoimmune encephalitis. He was also the founder member of the Walton Centre Clinical Neuroimmunology Group researching on autoantibody-associated neurological diseases.

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Anti-NMDA receptor encephalitis is a type of brain inflammation caused by antibodies. Early symptoms may include fever, headache, and feeling tired. This is then typically followed by psychosis which presents with false beliefs (delusions) and seeing or hearing things that others do not see or hear (hallucinations). People are also often agitated or confused. Over time, seizures, decreased breathing, and blood pressure and heart rate variability typically occur. In some cases, patients may develop catatonia.

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<span class="mw-page-title-main">Autoimmune encephalitis</span> Type of encephalitis

Autoimmune encephalitis (AIE) is a type of encephalitis, and one of the most common causes of noninfectious encephalitis. It can be triggered by tumors, infections, or it may be cryptogenic. The neurological manifestations can be either acute or subacute and usually develop within six weeks. The clinical manifestations include behavioral and psychiatric symptoms, autonomic disturbances, movement disorders, and seizures.

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References

  1. ↑ Rojas, Galeno; Demey, Ignacio; Quiroga, Julieta; Cejas, Luciana Leon; Bonardo, Pablo; Roca, Claudia Uribe; Parisi, Virginia Laura; Gatto, Emilia; Rugilo, Carlos; Ollari, Juan; Pardal, Manuel Fernandez (2016-04-05). "VGKC-Complex Antibody Encephalitis: Clinical Manifestations and Response to Immunotherapy (P2.251)". Neurology. 86 (16 Supplement). ISSN   0028-3878.
  2. 1 2 Hart IK, Waters C, Vincent A, Newland C, Beeson D, Pongs O, et al. (1997). "Autoantibodies detected to expressed K+ channels are implicated in neuromyotonia". Ann Neurol. 41 (2): 238–46. doi:10.1002/ana.410410215. PMID   9029073. S2CID   30375137.
  3. ↑ Vincent A (2008). "Autoimmune channelopathies: John Newsom-Davis's work and legacy. A summary of the Newsom-Davis Memorial Lecture 2008". J Neuroimmunol. 201–202: 245–9. doi:10.1016/j.jneuroim.2008.07.007. PMID   18722023. S2CID   28767520.
  4. 1 2 3 4 5 Irani SR, Alexander S, Waters P, Kleopa KA, Pettingill P, Zuliani L, et al. (2010). "Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan's syndrome and acquired neuromyotonia". Brain. 133 (9): 2734–48. doi:10.1093/brain/awq213. PMC   2929337 . PMID   20663977.
  5. ↑ Klein CJ, Lennon VA, Aston PA, McKeon A, O'Toole O, Quek A, et al. (2013). "Insights from LGI1 and CASPR2 potassium channel complex autoantibody subtyping". JAMA Neurol. 70 (2): 229–34. doi:10.1001/jamaneurol.2013.592. PMC   3895328 . PMID   23407760.
  6. 1 2 3 4 Lai M, Huijbers MG, Lancaster E, Graus F, Bataller L, Balice-Gordon R, et al. (2010). "Investigation of LGI1 as the antigen in limbic encephalitis previously attributed to potassium channels: a case series". Lancet Neurol. 9 (8): 776–85. doi:10.1016/S1474-4422(10)70137-X. PMC   3086669 . PMID   20580615.
  7. ↑ Irani SR, Michell AW, Lang B, Pettingill P, Waters P, Johnson MR, et al. (2011). "Faciobrachial dystonic seizures precede Lgi1 antibody limbic encephalitis". Ann Neurol. 69 (5): 892–900. doi:10.1002/ana.22307. PMID   21416487. S2CID   13775077.
  8. 1 2 3 4 Dalmau J, Rosenfeld MR (2014). "Autoimmune encephalitis update". Neuro Oncol. 16 (6): 771–8. doi:10.1093/neuonc/nou030. PMC   4022229 . PMID   24637228.
  9. ↑ Fukata Y, Lovero KL, Iwanaga T, Watanabe A, Yokoi N, Tabuchi K, et al. (2010). "Disruption of LGI1-linked synaptic complex causes abnormal synaptic transmission and epilepsy". Proc Natl Acad Sci U S A. 107 (8): 3799–804. Bibcode:2010PNAS..107.3799F. doi: 10.1073/pnas.0914537107 . PMC   2840530 . PMID   20133599.
  10. ↑ Gregor A, Albrecht B, Bader I, Bijlsma EK, Ekici AB, Engels H, et al. (2011). "Expanding the clinical spectrum associated with defects in CNTNAP2 and NRXN1". BMC Med Genet. 12: 106. doi: 10.1186/1471-2350-12-106 . PMC   3162517 . PMID   21827697.
  11. ↑ Vincent A, Buckley C, Schott JM, Baker I, Dewar BK, Detert N, et al. (2004). "Potassium channel antibody-associated encephalopathy: a potentially immunotherapy-responsive form of limbic encephalitis". Brain. 127 (Pt 3): 701–12. doi: 10.1093/brain/awh077 . PMID   14960497.
  12. ↑ Dalmau, J Rosenfeld, MR. Paraneoplastic and autoimmune encephalitis. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on October 11, 2015.)
  13. ↑ Somnier, F. E. (Apr 2015). Autoimmune encephalitis History & current knowledge (PDF). Copenhagen, Denmark: Statens Serum Institut. p. 6. Retrieved 2015-10-12.
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