LGI1 and CASPR2 Antibodies (Limbic Encephalitis screen), (Leucine-rich glioma-inactivated protein 1, Contactin-associated protein 2)

Immunology

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Description

 Patients with autoimmune encephalopathies may produce autoantibodies targeted towards neuronal surface antigens. Autoimmune encephalitis refers to a group of closely related diseases that share overlapping clinical features and have similar finding on brain imaging. The diseases can be differentiated by the presence of specific autoantibodies [1].

Neuromyotonia (Isaacs syndrome) is a rare and heterogenous syndrome of continuous motor unit activity of peripheral nerve origin that manifests as various combinations of muscle stiffness, cramps, twitching, weakness, and delayed muscle relaxation [2]. Although neuromyotonia may accompany an assortment of inherited diseases, most cases are acquired. The acquired form is often associated with an autoimmune disorder [2]. It is thought that autoantibodies to voltage-gated potassium channels produce the peripheral motor nerve hyperexcitability that characterizes neuromyotonia and thus establishes acquired neuromyotonia as an autoantibody-mediated disorder [3]. LGI1 and CASPR2 form part of the voltage gate potassium channel complex and are recognised as the antibody substrate in limbic encephalitis. Other proteins are involved in the voltage gated potassium channel complex and may have antibodies directed against them but these are not specific for limbic encephalitis..

The conditions present with symptoms such as seizures, confusion and other neuropsychiatric manifestations. Patients may have non-paraneoplastic or paraneoplastic associations. Diagnosis is usually made using a combination of clinical features, imaging and autoantibody detection. Early treatment results in considerable reduction of symptoms in most patients [1,4,5].

LGI1 and CASPR2 antibodies are now performed as the first line test, rather than checking for antibodies to the voltage gated potassium channel complex as the initial screen. 

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Indications

To aid in the diagnosis of autoimmune limbic encephalitis, neuromyotonia or Morvan’s syndrome. 

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Sample Type

2mL Serum (Gel 5mL Yellow tube) or CSF. Requests from outside Sheffield: Transport at ambient temperature via Royal Mail or Courier.

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Reference Range

Normal = Negative

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Turnaround Time

10 days

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Testing Frequency

Weekly

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References

Kelley BP, Patel SC, Marin HL, et al. Autoimmune Encephalitis: Pathophysiology and Imaging review of an overlooked diagnosis. American Journal of Neuroradiology. 2017. 38(6):1070-1078. [Ref 1] Shillito P, et al. Aquired neuromyotonia: evidence for autoantibodies directed against K+ channels of peripheral nerves. Ann Neuro. 1995. 38(5):714-722. [Ref 2] Newsom-Davis J and Mills KR. Immunological associations of acquired neuromyotonia (Isaacs' syndrome). Brain. 1993. 116(2): 453-469. [Ref 3] Lee SK. Lee ST. The laboratory diagnosis of autoimmune encephalitis. Journal of Epliepsy research. 2016. 6(2):45-52. [Ref 4]. Lancaster E. The diagnosis and treatment of autoimmune encephalitis. 2016. 12(1):1-13. [Ref 5].

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See Also

Cerebellar antibodies; NMDAR Antibodies; Autoimmune Encephalitis screen

Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.