Voltage-gated potassium channel complex antibodies in Creutzfeldt-Jakob disease

[Creutzfeldt-Jakob Disease Versus Anti-NMDA Receptor Encephalitis A Case Report]

Clinically differentiating between autoimmune and neurodegenerative disorders can often pose a diagnostic challenge. The differential diagnosis of rapidly progressing neurological and cognitive symptoms includes central nervous system tumours, cerebral vasculitis, and inflammatory, autoimmune, or paraneoplastic encephalopathies. Rarer neurodegenerative diseases such as Creutzfeldt-Jakob disease should also be considered. Detection of treatable causes, such as autoimmune disorders, remains important when potentially occurring in conjunction with Creutzfeldt-Jakob disease. The following report describes a rare case in which autoimmune encephalopathy and prion disease were considered as possible comorbidities.

Voltage-gated potassium channel blanket testing in first-episode psychosis: Diagnostic nihilism?

OBJECTIVE

Voltage-gated potassium channel antibodies are implicated in limbic encephalitis and currently included in first-episode psychosis organic screening guidelines. Individuals with high-positive voltage-gated potassium channel titres most commonly present with neurological symptoms as well as sleep, cognitive, behaviour, psychosis and mood disturbance. The significance of low-positive voltage-gated potassium channel antibody titres in psychiatric patients is unclear and has not been previously examined. We aim to describe a statewide cohort of psychiatric patients with low- and high-positive voltage-gated potassium channel titres and explore if this finding influenced clinical management and patient outcomes.

METHODS

A retrospective review of all voltage-gated potassium channel antibodies testing performed in public psychiatric services in Queensland, Australia, with comparison of the clinical presentation and long-term outcomes of low- and high-positive voltage-gated potassium channel titre cases. Specific antigen targets (leucine-rich glioma-inactivated protein 1 and contactin-associated protein 2 antibodies) were also assessed.

RESULTS

The overall prevalence of voltage-gated potassium channel antibody positivity in Queensland, public, psychiatric service testing was 0.3% (14/4098), with 12 cases of low-positive voltage-gated potassium channel titre, 2 cases of high-positive (leucine-rich glioma-inactivated protein 1 antibody positive) cases and a voltage-gated potassium channel negative contactin-associated protein 2 antibody positive case. No low-positive case developed neurological abnormalities or had abnormal paraclinical investigations. In comparison, both high-positive voltage-gated potassium channel/leucine-rich glioma-inactivated protein 1 cases and the contactin-associated protein 2 antibody positive case rapidly developed neurological symptoms, had abnormal paraclinical testing and improved only with immunotherapy. There was no later development of encephalitic symptoms in the low-positive cases over an average of 1067 days follow-up.

CONCLUSION

Voltage-gated potassium channel antibody-associated limbic encephalitis was rare, and always associated with high antibody titres. Low-positive titres were not associated with the development of encephalitis over a long period of follow-up. The value of universal voltage-gated potassium channel antibody screening is unclear, and further prospective studies in first-episode psychosis populations are required.

Antibodies to neuronal surface antigens in patients with a clinical diagnosis of neurodegenerative disorder

OBJECTIVES

Autoimmune encephalitis due to antibodies against neuronal surface antigens (NSA-Ab) frequently presents with cognitive impairment, often as the first and prevalent manifestation, but few studies have systematically assessed the frequency of NSA-Ab in consecutive patients with established neurodegenerative disorders.

METHODS

We studied sera of 93 patients (41F, 52 M), aged 69.2 ± 9.4 years, with neurodegenerative conditions, and of 50 population controls aged over 60 years. Specific NSA-Abs were investigated by antigen-specific cell-based assays (CBAs). After testing, we evaluated the association between the NSA-Abs and clinical, CSF and radiological features.

RESULTS

The patients included 13/93 (13.8%) who had specific antibodies to neuronal surface antigens: 6 GlyR, 3 GABA_AR (1 also positive for AMPAR), 2 LGI1, 1 CASPR2 and 1 GABA_BR. One of the 50 controls (2%) was positive for NMDAR antibody and the others were negative on all tests (P = 0.020). No difference was observed in antibody frequency between patients presenting with parkinsonism and those presenting with dementia (P = 0.55); however, NSA-Ab were more frequent in those with unclassified forms of dementia (5/13, 38.5%) than in those with unclassified parkinsonism (2/9, 22.2%) or with classified forms of dementia (4/43, 9.3%) or parkinsonism (2/28, 7.1%) (P = 0.03). A logistic regression analysis demonstrated that an unclassified diagnosis (P = 0.02) and an irregular progression (P = 0.024) were predictors of seropositive status.

CONCLUSIONS

NSA-Abs are relatively frequent in patients with neurodegenerative disorders, particularly in those with an irregular disease progression of atypical clinical features, inconsistent with a recognized diagnosis. The significance of these antibodies and their possible primary or secondary roles need to be investigated in prospective studies.

Voltage-Gated Potassium Channel Antibodies in Slow-Progression Motor Neuron Disease

BACKGROUND

The spectrum of autoimmune neurological diseases associated with voltage-gated potassium channel (VGKC)-complex antibodies (Abs) ranges from peripheral nerve disorders to limbic encephalitis. Recently, low titers of VGKC-complex Abs have also been reported in neurodegenerative disorders, but their clinical relevance is unknown.

OBJECTIVE

The aim of the study was to explore the prevalence of VGKC-complex Abs in slow-progression motor neuron disease (MND).

METHODS

We compared 11 patients affected by slow-progression MND with 9 patients presenting typical progression illness. Sera were tested for VGKC-complex Abs by radioimmunoassay. The distribution of VGKC-complex Abs was analyzed with the Mann-Whitney U test.

RESULTS

The statistical analysis showed a significant difference between the mean values in the study and control groups. A case with long-survival MND harboring VGKC-complex Abs and treated with intravenous immunoglobulins is described.

CONCLUSION

Although VGKC-complex Abs are not likely to be pathogenic, these results could reflect the coexistence of an immunological activation in patients with slow disease progression.

Creutzfeldt-Jakob disease mimicking autoimmune encephalitis with CASPR2 antibodies

Background

Differential diagnosis of severe progressive dementia includes a wide spectrum of inflammatory and neurodegenerative diseases. Particularly challenging is the differentiation of potentially treatable autoimmune encephalitis and Creutzfeldt-Jakob disease. Such a coincidence may indeed complicate the correct diagnosis and influence subsequent treatment.

Case presentation

A 75-year-old woman was admitted due to rapid progressive cognitive impairment. Her husband observed a temporal disorientation and confusion. The initial neurological examination and an extensive neuropsychological evaluation showed significant impairments in almost all tested cognitive domains. All other neurological functions including motor, sensory and coordinative function were intact. Initial diagnostics included EEG, MRI and lumbar puncture with unspecific results. Complementary blood testing revealed a positive result for antineural antibodies to Contactin-associated protein 2 (CASPR2) and the patient received treatment for CASPR2 autoimmune encephalitis. Further symptoms and results, including 14-3-3 proteins, led to suspected Creutzfeldt-Jakob disease. The postmortem examination supported the diagnosis of a definitive Creutzfeldt-Jakob disease.

Conclusion

One could argue that global screening for antineural antibodies may lead to a false diagnosis triggering intense and potentially dangerous procedures. We believe, however, that potentially treatable causes of dementia should aggressively sought out and subsequently treated in an attempt to curtail the course of disease and ultimately reduce the rate of mortality.

An 11-year retrospective experience of antibodies against the voltage-gated potassium channel (VGKC) complex from a tertiary neurological centre

Acquired diseases classically associated with VGKC-complex antibodies include peripheral nerve hyperexcitability (PNH), Morvan's syndrome, limbic encephalitis (LE), and epilepsy. However, not all such patients have VGKC-complex antibodies and antibodies have been reported in patients without a defined immune-mediated syndrome. To analyse the clinical relevance of positive VGKC-complex antibodies requested on the basis of initial clinical suspicion. We retrospectively analysed patients with positive VGKC-complex antibodies (>100 pM) referred to our institution between 2001 and 2011. 1,614 VGKC-complex assays were performed in 1,298 patients. Titres >100 pM were detected in 57/1,298 (4 %) patients. A classic VGKC-complex channelopathy (60 %) was associated with VGKC-complex antibody titres >400 pM (p = 0.0004). LGI1 or CASPR2 antibodies were only detected in classic VGKC-complex channelopathies (LE; n = 3/4 and PNH; n = 1/5). VGKC-complex antibody titres <400 pM were seen with PNH (n = 15/22; 68 %) but also a heterogeneous range of central and/or peripheral nervous system disorders. Electromyography was supportive of PNH in 65 % of cases and symptomatic treatment was beneficial in 46 % of patients. Irrespective of titre, the rate of malignancy in patients with VGKC-complex antibodies was higher than the age-matched national incidence of malignancy (OR 19.9, 95 % CI 8.97-44.0 p<0.0001). Clinical phenotyping and antibody titres >400 pM can help determine VGKC-complex antibody relevance. Antibody titres <400 pM are associated with PNH but also a more heterogeneous clinical spectrum. The antibody association in the latter is of doubtful clinical relevance. The rate of malignancy was significantly higher than the national incidence irrespective of titre.

Autoimmune encephalopathies

Over the past 10 years, the continual discovery of novel forms of encephalitis associated with antibodies to cell-surface or synaptic proteins has changed the paradigms for diagnosing and treating disorders that were previously unknown or mischaracterized. We review here the process of discovery, the symptoms, and the target antigens of 11 autoimmune encephalitic disorders, grouped by syndromes and approached from a clinical perspective. Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, several subtypes of limbic encephalitis, stiff-person spectrum disorders, and other autoimmune encephalitides that result in psychosis, seizures, or abnormal movements are described in detail. We include a novel encephalopathy with prominent sleep dysfunction that provides an intriguing link between chronic neurodegeneration and cell-surface autoimmunity (IgLON5). Some of the caveats of limited serum testing are outlined. In addition, we review the underlying cellular and synaptic mechanisms that for some disorders confirm the antibody pathogenicity. The multidisciplinary impact of autoimmune encephalitis has been expanded recently by the discovery that herpes simplex encephalitis is a robust trigger of synaptic autoimmunity, and that some patients may develop overlapping syndromes, including anti-NMDAR encephalitis and neuromyelitis optica or other demyelinating diseases.

Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease

Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is the rare instance when a positive VGKC complex antibody titre occurs in a definite case of prion disease. We present a pathologically and genetically confirmed case of CJD with elevated serum VGKC complex antibody titres. This case highlights the importance of interpreting the result of a positive VGKC complex antibody with caution and in the context of the overall clinical manifestation.

Clinical relevance of positive voltage-gated potassium channel (VGKC)-complex antibodies: experience from a tertiary referral centre

BACKGROUND

Voltage-gated potassium channel (VGKC)-complex antibodies can be associated with a range of immunotherapy-responsive clinical presentations including limbic encephalitis, Morvan's syndrome and acquired neuromyotonia. However, there are patients with positive levels in whom the significance is uncertain.

OBJECTIVE

To evaluate the clinical significance associated with positive (>100 pM) VGKC-complex antibodies.

METHODS

Over a 4-year period, 1053 samples were sent for testing of which 55 were positive. The clinical presentations, final diagnoses and responses to immunotherapies, when given, were assessed retrospectively and the likelihood of autoimmunity was categorised as definite, possible, unlikely or undetermined (modified from Zuliani et al 2012).

RESULTS

Only 4 of the 32 patients with low-positive (100-400 pM) levels were considered definitely autoimmune, 3 with peripheral nerve hyperexcitability and 1 with a thymoma; 3 were given immunotherapies. Of the remaining 28 with low-positive levels, 13 (3 of whom had tumours) were considered possibly autoimmune, and 15 were unlikely or undetermined; 1 was given immunotherapy unsuccessfully. Of the 23 patients with high-positive (>400 pM) levels, 12 were given immunotherapies, 11 of whom showed a good response. 11 were considered definitely autoimmune, 10 with limbic encephalitis (antibody specificity: 5 LGI1, 1 contactin2, 2 negative, 2 untested) and 1 with a tumour. In the remaining 12, autoimmunity was considered possible (n=9; most had not received immunotherapies), or unlikely (n=3).

CONCLUSIONS

As antibody testing becomes more widely available, and many samples are referred from patients with less clear-cut diagnoses, it is important to assess the utility of the results. VGKC-complex antibodies in the range of 100-400 pM (0.1-0.4 nM) were considered clinically relevant in rare conditions with peripheral nerve hyperexcitability and appeared to associate with tumours (12.5%). By contrast high-positive (>400 pM; >0.4 nM) levels were considered definitely (38%) or possibly (49%) clinically relevant, but not all patients had a 'classical' limbic encephalitis and some did not receive immunotherapies.

Determination of neuronal antibodies in suspected and definite Creutzfeldt-Jakob disease

IMPORTANCE

Creutzfeldt-Jakob disease (CJD) and autoimmune encephalitis with antibodies against neuronal surface antigens (NSA-abs) may present with similar clinical features. Establishing the correct diagnosis has practical implications in the management of care for these patients.

OBJECTIVE

To determine the frequency of NSA-abs in the cerebrospinal fluid of patients with suspected CJD and in patients with pathologically confirmed (ie, definite) CJD.

DESIGN, SETTING, AND PARTICIPANTS

A mixed prospective (suspected) and retrospective (definite) CJD cohort study was conducted in a reference center for detection of NSA-abs. The population included 346 patients with suspected CJD and 49 patients with definite CJD.

MAIN OUTCOMES AND MEASURES

Analysis of NSA-abs in cerebrospinal fluid with brain immunohistochemistry optimized for cell-surface antigens was performed. Positive cases in the suspected CJD group were further studied for antigen specificity using cell-based assays. All definite CJD cases were comprehensively tested for NSA-abs, with cell-based assays used for leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein-like 2 (CASPR2), N-methyl-d-aspartate (NMDA), and glycine (GlY) receptors.

RESULTS

Neuronal surface antigens were detected in 6 of 346 patients (1.7%) with rapid neurologic deterioration suggestive of CJD. None of these 6 patients fulfilled the diagnostic criteria for probable or possible CJD. The target antigens included CASPR2, LGI1, NMDAR, aquaporin 4, Tr (DNER [δ/notch-like epidermal growth factor-related receptor]), and an unknown protein. Four of the patients developed rapidly progressive dementia, and the other 2 patients had cerebellar ataxia or seizures that were initially considered to be myoclonus without cognitive decline. The patient with Tr-abs had a positive 14-3-3 test result. Small cell lung carcinoma was diagnosed in the patient with antibodies against an unknown antigen. All patients improved or stabilized after appropriate treatment. None of the 49 patients with definite CJD had NSA-abs.

CONCLUSIONS AND RELEVANCE

A low, but clinically relevant, number of patients with suspected CJD had potentially treatable disorders associated with NSA-abs. In contrast, none of 49 patients with definite CJD had NSA-abs, including NMDAR-abs, GlyR-abs, LGI1-abs, or CASPR2-abs. These findings suggest that cerebrospinal fluid NSA-abs analysis should be included in the diagnostic workup of patients with rapidly progressive central nervous system syndromes, particularly when they do not fulfill the diagnostic criteria of probable or possible CJD.

Clinical spectrum and diagnostic value of antibodies against the potassium channel related protein complex

INTRODUCTION

Antibodies against a protein complex that includes voltage-gated potassium channels (VGKC) have been reported in patients with limbic encephalitis, peripheral nerve hyperexcitability, Morvan's syndrome, and a large variety of neurological syndromes.

REVIEW SUMMARY

In this article, a review is presented of the syndromes associated with antibodies against VGKC-related proteins and the main antigens of this protein complex, the proteins LGI1 (leucine rich glioma inactivated protein 1) and Caspr2 (contactin-associated protein-like 2). The conceptual problems and clinical implications of the description of antibodies against VGKC-related proteins other than LGI1 and Caspr2 are also discussed. Although initial studies indicated the occurrence of antibodies against VGKC, recent investigations have shown that the main antigens are a neuronal secreted protein known as LGI1 which modulates synaptic excitability, and a protein called Caspr2 located on the cell surface and processes of neurons of different brain regions, and at the juxtaparanodal region of myelinated axons. While antibodies against LGI1 preferentially associate with classical limbic encephalitis, antibodies against Caspr2 associate with a wider spectrum of symptoms, including Morvan's syndrome, peripheral nerve hyperexcitability or neuromyotonia, and limbic or more extensive encephalitis. In addition there are reports of patients with antibodies against VGKC-related proteins that are different from LGI1 or Caspr2. In these cases, the identity and location of the antigens are unknown, the syndrome association is not specific, and the response to treatment uncertain.

CONCLUSIONS

The discovery of antigens such as LGI1 and Caspr2 has resulted in a clinical and molecular definition of the broad group of diseases previously attributed to antibodies against VGKC. Considering the literature that describes the presence of antibodies against VGKC other than LGI1 and Caspr2 proteins, we propose a practical algorithm for the diagnosis and treatment of these patients.