Clinical utility of seropositive voltage-gated potassium channel-complex antibody

Anti-N-Methyl-D-Aspartate (NMDA) Receptor Encephalitis Secondary to an Ovarian Dermoid Cyst

Dermoid cysts, or mature cystic teratomas, are germ cell neoplasms that can arise on the ovaries. Being of germ cell origin, such cysts can have extensive variance in presentation, including a rare paraneoplastic effect where they produce N-methyl-D-aspartate receptor (NMDAR) antibodies, resulting in anti-NMDAR encephalitis. This can cause various neuropsychiatric symptoms, including confusion, hallucinations, psychosis, disorientation, and a change in cognition. This case study presents the unusual occurrence of a 39-year-old female patient who presented to the emergency department with encephalitis, headaches, and auditory hallucinations after recent glucocorticoid use. Through an extensive workup, imaging, and various physician consults, the patient was diagnosed with anti-NMDAR encephalitis secondary to a paraneoplastic effect originating from an ovarian dermoid cyst.

Mercury Induced Autoimmunity: A Case of CASPR2/LGI1 Autoimmune Encephalitis in a 14-Month-old

Contactin-associated protein-like 2 (CASPR2) autoantibodies are among those associated with several syndromes with effects on both the central and peripheral nervous systems including neuropathy and encephalitis and is most commonly seen in middle-aged to elderly males. We present a case of autoimmune encephalitis in a 14-month-old female presenting with altered mental status, refusal to bear weight, and hypertension in the setting of mercury exposure. This is the youngest reported case of CASPR2/LGI1/VGKC antibody associated autoimmune encephalitis stimulated by mercury exposure.

Occult bowel cancer presenting as Morvan syndrome

A man in his mid-60s presented with a 3-month history of progressive muscle twitching, agitation, cognitive impairment, insomnia, hyperhidrosis and lower limb pain. He had fasciculations, myokymia, myoclonus, exaggerated startle response and significant postural hypotension. Electrophysiological studies showed evidence of peripheral nerve hyperexcitability with neuromyotonia. Contactin-associated protein-like 2 antibodies (CASPR2) were strongly positive. A diagnosis of Morvan syndrome was made. CT of the chest, abdomen and pelvis was undertaken to identify any occult malignancy, and a large bowel carcinoma in situ was identified and resected. His central nervous system and autonomic symptoms significantly improved following surgery, but neuromyotonia persisted, and this was treated with intravenous immunoglobulins and steroids. Early detection of bowel cancer in this patient enabled curative treatment.

Rapidly Progressive Paraneoplastic Neuropathy Associated with Renal Cell Carcinoma: A Case Report

Background

Paraneoplastic neurological disorders are rare syndromes that occur with various malignancies including renal cell carcinoma. Symptoms of paraneoplastic neurological disorders are diverse and involve either the central nervous system, peripheral nervous system, or both.

Case Presentation

We present a patient with diffuse limb pain, rapidly progressive asymmetric motor and sensory symptoms and distal upper limb atrophy. Electrodiagnostic testing was suggestive of mononeuritis multiplex. Initial empiric treatment with corticosteroids did not lead to improvement. Further diagnostic studies revealed bilateral clear cell renal carcinoma. Treatment with plasmapheresis led to significant and rapid improvement in pain and limb strength.

Conclusions

This case highlights the rare occurrence of paraneoplastic neuropathy in renal cancer and emphasizes the importance of screening for malignancy in patients presenting with rapidly progressive multifocal neuropathy.

Autoimmune Limbic Encephalitis: A Review of Clinicoradiological Features and the Challenges of Diagnosis

Limbic encephalitis is an autoimmune cause of encephalitis. In addition to the usual symptoms of encephalitis such as altered consciousness, fever, and focal neurological deficits, limbic encephalitis can present with neuropsychiatric manifestations and seizures. Making a formal diagnosis involves a difficult and prolonged workup phase. The purpose of this review is to help readers delineate limbic encephalitis from other illnesses. This is done by presenting a spectrum of potential organic differential diagnoses and pertinent findings that distinguish them from limbic encephalitis. Instead of presenting a variety of psychiatric differential diagnoses, the authors present a review of psychiatric manifestations known to be associated with limbic encephalitis, as naturally, any psychiatric disorder could be a potential comorbid disease.

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.

Autoimmune encephalitis: proposed recommendations for symptomatic and long-term management

The objective of this paper is to evaluate available evidence for each step in autoimmune encephalitis management and provide expert opinion when evidence is lacking. The paper approaches autoimmune encephalitis as a broad category rather than focusing on individual antibody syndromes. Core authors from the Autoimmune Encephalitis Alliance Clinicians Network reviewed literature and developed the first draft. Where evidence was lacking or controversial, an electronic survey was distributed to all members to solicit individual responses. Sixty-eight members from 17 countries answered the survey. The most popular bridging therapy was oral prednisone taper chosen by 38% of responders while rituximab was the most popular maintenance therapy chosen by 46%. Most responders considered maintenance immunosuppression after a second relapse in patients with neuronal surface antibodies (70%) or seronegative autoimmune encephalitis (61%) as opposed to those with onconeuronal antibodies (29%). Most responders opted to cancer screening for 4 years in patients with neuronal surface antibodies (49%) or limbic encephalitis (46%) as opposed to non-limbic seronegative autoimmune encephalitis (36%). Detailed survey results are presented in the manuscript and a summary of the diagnostic and therapeutic recommendations is presented at the conclusion.

Evaluating the frequency of positive paraneoplastic antibodies and associated malignancy risk

OBJECTIVE

To evaluate the association between malignancy and frequently positive paraneoplastic antibodies.

METHODS

A retrospective cohort study was carried out for all patients who received paraneoplastic antibody testing in 2013-2014 at a tertiary referral center. Available medical records on included patients were reviewed through July 2020. Patients were divided into antibody positive and negative subgroups. Focused analysis was performed on the subgroup of patients who received testing via a commonly used antibody panel.

RESULTS

A total of 1860 patients (the full cohort) received 19,323 antibody testing via panel or individual antibody testing, and were followed-up for a mean period of 36.2 months (range 0-83 months). Altogether 229 antibodies in 196 patients were positive, and 9 (3.9%) in 7 patients were against onconeuronal antigens. The remaining 220 (96.1%) were positive for mostly antibodies against cell surface or synaptic antigens. A total of 1161 patients received Mayo Clinic paraneoplastic antibody panel tests (the panel cohort), and 14.9% (173) of these patients possessed one or more positive antibodies. For the panel cohort, no difference was found between antibody positive and negative groups with respect to the prevalence of previously existing malignancy (15.6% versus 16.6%, p = 0.745) or incidence of new malignancy (4.0% vs. 3.7%, p = 0.848) during the follow-up period. No difference was observed in the incidence of new malignancy during follow-up between the antibody positive and negative groups for the 7 most frequently positive antibodies.

CONCLUSIONS

The presence of frequently positive antibodies, mostly to cell surface or synaptic antigens, is not clearly associated with the development of malignancy in the subsequent three years.

Confounders in the Interpretation of Paraneoplastic and Neuronal Autoantibody Panels

The recent discovery of several neuronal autoantibodies linked to neurologic syndromes that are fully or partially responsive to immunosuppressive therapy has revolutionized neuroimmunology and expanded the scope of classical paraneoplastic and antibody-related syndromes. A great deal of understanding of the techniques of neuronal antibody testing, the sensitivity and specificity of serum and cerebrospinal fluid sampling, and the value of the specific type and titer of each antibody is imperative. This article provides an overview of neuronal antibody and paraneoplastic panel testing with emphasis on how to differentiate clinically relevant from clinically irrelevant results and the downstream implications of those results.

Stop testing for autoantibodies to the VGKC-complex: only request LGI1 and CASPR2

Autoantibodies to leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein like-2 (CASPR2) are associated with clinically distinctive syndromes that are highly immunotherapy responsive, such as limbic encephalitis, faciobrachial dystonic seizures, Morvan’s syndrome and neuromyotonia. These autoantibodies target surface-exposed domains of LGI1 or CASPR2, and appear to be directly pathogenic. In contrast, voltage-gated potassium channel (VGKC) antibodies that lack LGI1 or CASPR2 reactivities (‘double-negative’) are common in healthy controls and have no consistent associations with distinct syndromes. These antibodies target intracellular epitopes and lack pathogenic potential. Moreover, the clinically important LGI1 and CASPR2 antibodies comprise only ~15% of VGKC-positive results, meaning that most VGKC-antibody positive results mislead rather than help. Further, initial VGKC testing misses some cases that have LGI1 and CASPR2 antibodies. These collective observations confirm that laboratories should stop testing for VGKC antibodies and instead, test only for LGI1 and CASPR2 antibodies. This change in practice will lead to significant patient benefit.

Glioblastoma as an autoimmune limbic encephalitis mimic: A case and review of the literature

A 43-year-old woman presented with cognitive decline, focal seizures, brain MRI showing non-enhancing, bilateral hippocampal lesions, but normal cerebrospinal fluid findings, which fulfilled the Graus et al., 2016 criteria for autoimmune limbic encephalitis (ALE). Subjective improvements were observed after immunotherapy. A repeat brain MRI showed new contrast enhancement and positron emission tomography revealed left hippocampal uptake. Biopsy of the right parahippocampus yielded high-grade glioma. Five similar cases, among the 14 with unilateral hippocampal lesions on MRI, were identified in the literature whereby suspected ALE preceded the high-grade glioma diagnosis. Gliomas confined to hippocampi can have clinical features overlapping with ALE.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice - Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Eighth Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating and categorizing indications for the evidence-based use of therapeutic apheresis (TA) in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Eighth Edition of the JCA Special Issue continues to maintain this methodology and rigor in order to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Eighth Edition, like its predecessor, continues to apply the category and grading system definitions in fact sheets. The general layout and concept of a fact sheet that was introduced in the Fourth Edition, has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of TA in a specific disease entity or medical condition. The Eighth Edition comprises 84 fact sheets for relevant diseases and medical conditions, with 157 graded and categorized indications and/or TA modalities. The Eighth Edition of the JCA Special Issue seeks to continue to serve as a key resource that guides the utilization of TA in the treatment of human disease.

Peripheral Nerve Hyperexcitability Syndromes

PURPOSE OF REVIEW

This article provides a review of the clinical phenotypes and evaluation of peripheral nerve hyperexcitability syndromes. These rare diagnoses include cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. Recent investigations have led to an understanding of the autoimmune underpinnings of these conditions and their specific associated antibodies. As the presentation of peripheral nerve hyperexcitability syndromes includes muscle stiffness, twitches, and spasms, which are also shared with certain central nervous system and myopathic conditions, the differential diagnosis of peripheral nerve hyperexcitability syndromes is reviewed.

RECENT FINDINGS

Peripheral nerve hyperexcitability syndromes share clinical and electrodiagnostic evidence of motor nerve instability; however, their clinical presentations are varied. Case reviews have helped us understand the spectrum of symptoms associated with the three peripheral nerve hyperexcitability syndromes reviewed here: cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. More recently, research has focused on understanding the voltage-gated potassium channel complex antibodies as well as neoplasms associated with these conditions.

SUMMARY

The diagnosis of peripheral nerve hyperexcitability syndromes requires a high index of suspicion, support from the physical examination, familiarity with the spectrum of symptoms associated with peripheral nerve hyperexcitability syndromes, and recognition of diagnostic EMG features. Voltage-gated potassium channel complex antibodies are associated with these conditions. Optimum treatment and autoimmune pathogenesis remain areas of active research.

Autoimmune encephalitis with anti-leucine-rich glioma-inactivated 1 or anti-contactin-associated protein-like 2 antibodies (formerly called voltage-gated potassium channel-complex antibodies)

PURPOSE OF REVIEW

Twenty years since the discovery of voltage-gated potassium channel (VGKC)-related autoimmunity; it is currently known that the antibodies are not directed at the VGKC itself but to two closely associated proteins, anti-leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (Caspr2). Antibodies to LGI1 and Caspr2 give well-described clinical phenotypes. Anti-LGI1 encephalitis patients mostly have limbic symptoms, and anti-Caspr2 patients have variable syndromes with both central and peripheral symptoms. A large group of patients with heterogeneous symptoms are VGKC positive but do not have antibodies against LGI1 or Caspr2. The clinical relevance of VGKC positivity in these 'double-negative' patients is questionable. This review focusses on these three essentially different subgroups.

RECENT FINDINGS

The clinical phenotypes of anti-LGI1 encephalitis and anti-Caspr2 encephalitis have been described in more detail including data on treatment and long-term follow-up. A specific human leukocyte antigen (HLA) association was found in nontumor anti-LGI1 encephalitis, but not clearly in those with tumors. There has been increasing interest in the VGKC patients without LGI1/Caspr2 antibodies questioning its relevance in clinical practice.

SUMMARY

Anti-LGI1 encephalitis and anti-Caspr2 encephalitis are separate clinical entities. Early recognition and treatment is necessary and rewarding. The term VGKC-complex antibodies, lumping patients with anti-LGI1, anti-Caspr2 antibodies or lacking both, should be considered obsolete.