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1.
Stop testing for autoantibodies to the VGKC-complex: only request LGI1 and CASPR2.
Michael, S, Waters, P, Irani, SR
Practical neurology. 2020;(5):377-384
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Abstract
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.
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2.
Autoimmune Vestibulocerebellar Syndromes.
Narayan, RN, McKeon, A, Fife, TD
Seminars in neurology. 2020;(1):97-115
Abstract
Autoimmune disorders affecting the vestibular end organs, vestibular pathways, vestibular nuclei, and vestibulocerebellum are often underrecognized as a cause of chronic dizziness and ataxia. Autoantibodies specific for cell-surface, synaptic, and intracellular neural antigens serve as biomarkers of these disorders. This article describes the epidemiology, clinical presentation, diagnostic considerations, imaging findings, treatment, and prognosis of autoimmune disorders, in which the vestibulocerebellar syndrome is the main or presenting clinical presentation. Antibodies specific for intracellular antigenic targets described in the article are PCA-1 (Purkinje cell cytoplasmic antibody type 1, also known as anti-Yo), ANNA-1 (antinuclear neuronal antibody type 1, also known as anti-Hu), ANNA-2 (antinuclear neuronal antibody type 2, also known as anti-Ri), Ma1/2 (anti-Kelch-like 11/12 antibody), Kelch-like 11, amphiphysin, CV2 (collapsin response 2, also known as collapsin response mediator protein-5 [CRMP5]), VGCC (voltage-gated calcium channel), GAD65 (glutamic acid decarboxylase 65-kDa isoform), AP3B2 (adaptor protein 3B2, also known as anti-Nb), MAP1B (microtubule-associated protein 1B antibody, also known as anti-PCA-2), and neurochondrin antibodies. Antibodies targeting cell-surface or synaptic antigenic targets described in the article include DNER (delta/notchlike epidermal growth factor related receptor; antigen to anti-Tr), CASPR2 (contactin-associated proteinlike 2), septin-5, Homer-3, and mGluR1 (metabotropic glutamate receptor 1). The vestibulocerebellar presentation is largely indistinguishable among these conditions and is characterized by subacute onset of cerebellar symptoms over weeks to months. The diagnosis of autoimmune vestibulocerebellar syndromes is based on a combination of clinical and serological features, with a limited role for neuroimaging. Subtle eye movement abnormalities can be an early feature in many of these disorders, and therefore a meticulous vestibulo-ocular examination is essential for early and correct identification. Cancer occurrence and its type are variable and depend on the autoantibody detected and other cancer risk factors. Treatment comprises immunotherapy and cancer-directed therapy. Acute immunotherapies such as intravenous immunoglobulin, plasma exchange, and steroids are used in the initial phase, and the use of long-term immunosuppression such as rituximab may be necessary in relapsing cases. Outcomes are better if immunotherapy is started early. The neurologic prognosis depends on multiple factors.
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3.
Neuronal Surface Antibody Syndrome: A Review of the Characteristics of the Disease and Its Association with Autoantibodies.
Liu, R, Zhang, M, Liu, L, Chen, G, Hou, Y, Wang, M, Li, J
Neuroimmunomodulation. 2020;(1):1-8
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Abstract
Several studies have certified that autoantibodies play an important role in the manifestation of neuromuscular diseases. Scientists have discovered specific neuronal tumor antibodies in patients with typical paraneoplastic neurological disorders. But in some clinical cases, it is not useful to cure this disease with common treatments unless the autoantibodies are addressed. In addition, recent studies have shown a close relationship between certain antibodies and neuronal surface proteins in some special cases. These antibodies, which act on the surface of neurons, mainly include voltage-gated calcium channel (VGKC) antibodies. VGKC antibodies are further divided into several types including anti-leucine-rich glioma inactivated 1 (LGI1), anti-contactin-associated protein-like 2 (Caspr2), anti-N-methyl-D-aspartate receptor (NMDAR), anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), anti-γ-aminobutyric acid receptor (GABAR), and glycine receptor. For the purpose of this review, cases of clinical studies of autoantibody-associated encephalitis were collected, the key points regarding the pathogenesis were summarized, the clinical manifestation was discussed, and all this information was organized as this review in order to introduce the relationship between autoantibodies and autoimmune encephalitis. Furthermore, it is hoped that it can effectively direct the development of diagnostic and therapeutic approach in the future.
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4.
The Clinical Value and Variation of Antithyroid Antibodies during Pregnancy.
Li, C, Zhou, J, Huang, Z, Pan, X, Leung, W, Chen, L, Zhang, Y, Wang, L, Sima, Y, Gober, HJ, et al
Disease markers. 2020;:8871951
Abstract
Antithyroid antibodies, which include thyroid-stimulating hormone receptor antibodies (TRAbs), thyroid peroxidase antibodies (TPOAbs), and thyroid globulin antibodies (TgAbs), are widely known for their tight association with thyroid autoimmune diseases. The variation in all three kinds of antibodies also showed different trends during and after pregnancy (Weetman, 2010). This article reviewed the the physiological changes, while focusing on the variation of thyroid antibodies concentration in women during and after pregnancy, and adverse consequences related to their elevation. Since abnormal elevations of these antithyroid antibodies may lead to adverse outcomes in both mothers and fetuses, special attention must be paid to the titer of the antibodies during pregnancy. The molecular mechanisms of the variations in those antibodies have yet to be explained. The frequency and timing of thyroid antibody measurement, as well as different reference levels, also remain to be elucidated.
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5.
Graves' disease in clinical perspective.
Ehlers, M, Schott, M, Allelein, S
Frontiers in bioscience (Landmark edition). 2019;(1):35-47
Abstract
Graves' disease (GD) is the most common cause for hyperthyroidism in iodine-replete areas. The disease is caused by the appearance of stimulating TSH receptor autoantibodies (TRAb) leading to hyperthyroidism. Blocking and neutral TRAb have, however, also been described. TRAb can be measured either by competition assays, assays using a bridge technology or bioassays (for discriminating stimulating vs. blocking antibodies). Therapy of GD with antithyroid drugs belonging to the group of thionamides is the first-line treatment to be continued for 12 up to 18 months. In case of relapse, thyroid ablative therapy including radioiodine therapy or thyroidectomy, respectively, should be performed. Risk factors for relapse are a large thyroid volume, persistence of high TRAb serum titer, smoking, and others. Within this review, we will give insights into the pathogenesis of GD including the pathogenesis of Graves' ophthalmopathy. We also describe recent developments of TRAb measurement, which is used for the diagnosis of GD as well as for outcome prediction. Finally, we discuss therapy aspects as well as the important issue of GD and pregnancy.
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6.
The structure, specificity and function of anti-citrullinated protein antibodies.
Ge, C, Holmdahl, R
Nature reviews. Rheumatology. 2019;(8):503-508
Abstract
In this Perspectives article, we outline a proposed model for understanding the specificity and function of anti-citrullinated protein antibodies (ACPAs). We suggest that ACPAs vary in specificity between two extremes: some are 'promiscuous' in that they are highly specific for the citrulline side chain, but cross-react with a range of citrullinated peptides, whereas others are 'private' in that their recognition of citrulline as well as proximal amino acid side chains enables protein-specific interactions. Promiscuous ACPAs tend to dominate in the sera both before and after the onset of rheumatoid arthritis, but their functional role has not been clarified. No firm evidence exists that these ACPAs are pathogenic. By contrast, private ACPAs encompass antibodies that specifically recognize citrullinated epitopes on joint proteins or that cross-react with joint proteins, thereby opening up the possibility that these private ACPAs are arthritogenic. These joint-reactive antibodies are more likely to target joints by binding to joint tissues and to promote the formation of local immune complexes leading to bone erosions, pain and arthritis.
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7.
SYNDROMES OF KETOSIS-PRONE DIABETES.
Balasubramanyam, A
Transactions of the American Clinical and Climatological Association. 2019;:145-155
Abstract
Ketosis-prone diabetes (KPD) is a heterogeneous condition characterized by patients who present with diabetic ketoacidosis but lack the phenotype of autoimmune type 1 diabetes. Here I review progress in our understanding of KPD and its place in the expanding universe of "atypical diabetes." I focus on investigations of our collaborative research group at Baylor College of Medicine and the University of Washington using a longitudinally followed, heterogeneous, multiethnic cohort of KPD patients. We have identified clinically and pathophysiologically distinct KPD subgroups, separable by the presence or absence of islet autoimmunity and the presence or absence of beta cell functional reserve. The resulting "Aß" classification of KPD accurately predicts long-term glycemic control and insulin dependence. I describe key characteristics of the KPD subgroups, their natural histories, and our investigations into their immunologic, genetic, and metabolic etiologies. These studies serve as a paradigm for the investigation of atypical forms of diabetes.
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8.
Type 1 Diabetes-related Autoantibodies in Different Forms of Diabetes.
Sørgjerd, EP
Current diabetes reviews. 2019;(3):199-204
Abstract
Autoantibodies against Glutamic Acid Decarboxylase (GADA), insulinoma antigen-2 (IA- 2A), insulin (IAA) and the most recently Zinc Transporter 8 (ZnT8A) are one of the most reliable biomarkers for autoimmune diabetes in both children and adults. They are today the only biomarkers that can distinguish Latent Autoimmune Diabetes in Adults (LADA) from phenotypically type 2 diabetes. As the frequency of autoantibodies at diagnosis in childhood type 1 diabetes depends on age, GADA is by far the most common in adult onset autoimmune diabetes, especially LADA. Being multiple autoantibody positive have also shown to be more common in childhood diabetes compared to adult onset diabetes, and multiple autoantibody positivity have a high predictive value of childhood type 1 diabetes. Autoantibodies have shown inconsistent results to predict diabetes in adults. Levels of autoantibodies are reported to cause heterogeneity in LADA. Reports indicate that individuals with high levels of autoantibodies have a more type 1 diabetes like phenotype and individuals with low levels of autoantibody positivity have a more type 2 diabetes like phenotype. It is also well known that autoantibody levels can fluctuate and transient autoantibody positivity in adult onset autoimmune diabetes have been reported to affect the phenotype.
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9.
[Three cases report of juvenile dermatomyositis with positive anti-melanoma differentiation associated gene 5 (MDA5) antibody and severe interstitial lung disease and literature review].
Hou, J, Zhou, ZX, Li, JG, Xu, YJ, Ding, YC
Zhonghua er ke za zhi = Chinese journal of pediatrics. 2019;(12):928-933
Abstract
Objective: To report the clinical features of anti-MDA5 antibody positive juvenile dermatomyositis (JDM) complicated with severe interstitial lung disease (ILD). Methods: The clinical data of three patients, who was admitted to the Department of Rheumatology and Immunology, Children's Hospital of the Capital Institute of Pediatrics from September 2016 to July 2017, with anti-melanoma differentiation associated gene 5 (MDA5) antibody positive JDM complicated with ILD were retrospectively extracted and analyzed. Meanwhile, PubMed database, CNKI, Wanfang database and China Biology Medicine disc (from their establishment to February 2019) with the key words "juvenile dermatomyositis" "interstitial lung disease" , and "anti-MAD5 antibody" both in English and Chinese were searched. Results: There were 2 females and 1 male (P1-P3), aged from 10 years 3 months to13 years 4 months, the time from onset to diagnosis were 2 months, 4 months and 10 months. All presented with rash. One of them had decreased muscle strength, and two had decreased activity tolerance. Creatine kinase was 588, 915 and 74 U/L, and serum ferritin were 1 792, >2 000 and 195.4 μg/L. All three patients had positive anti-MDA5 antibodies. At the time of diagnosis, all of them had ILD, pneumothorax and mediastinal emphysema, but had no respiratory symptoms. All three patients received oral methylprednisolone and cyclophosphamide pulse therapy, while human immunoglobulin was given only to P1 and P2. P1 developed rapid progressive pulmonary interstitial disease (RPILD) and died of respiratory failure after 2 months. While P2 and P3 were followed up for 1 to 2 years, who had complete remission, as anti-MDA5 antibody turned to negative and ILD improved significantly. Ten related reports in literature were retrieved, without reported Chinese cases, and most cases initiated with rash and very likely complicated with arthritis. Some of them were more likely to have ILD rather than muscle weakness. It also showed that Japanese JDM children had higher rate of positive anti-MDA5 antibody than patients from the U.S. and U.K., and are more susceptible to ILD and RPILD. The mortality rate of patients with RPILD is extremely high. Conclusions: The cases of JDM with positive anti-MDA5 antibody mainly presented with rash and mild muscle weakness, and could be complicated with ILD, pneumothorax and mediastinal emphysema without respiratory symptoms at early stage. Anti-MDA5 antibody titer is related to disease activity and can turn to negative after treatment.
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10.
Peroxynitrite: cellular pathology and implications in autoimmunity.
Ahmad, R, Hussain, A, Ahsan, H
Journal of immunoassay & immunochemistry. 2019;(2):123-138
Abstract
In inflamed tissues, the reaction of nitric oxide and superoxide leads to the formation of an extremely reactive peroxynitrite (ONOO-), which is a well known oxidizing and nitrating agent that exhibits high reactivity at physiological pH. The peroxynitrite formed can attack a wide range of biomolecules via direct oxidative reactions or indirect radical-mediated mechanisms thus triggering cellular responses leading to cell signaling, oxidative injury, committing cells to necrosis or apoptosis. Cellular DNA is an important target for ONOO- attack, and can react with deoxyribose, nucleobases or induces single strand breaks. The free radical-mediated damage to proteins results in the modification of amino acid residues, cross-linking of side chains and fragmentation. Free/protein-bound tyrosines are attacked by various reactive nitrogen species (RNS), including peroxynitrite, to form free/protein-bound nitrotyrosine (NT). The formation of NT represents a specific peroxynitrite-mediated protein modification, and the detection of NT in proteins is considered as a biomarker for endogenous peroxynitrite activity. The peroxynitrite-driven oxidation and nitration of biomolecules may lead to autoimmunity and age-related neurodegenerative diseases. Hence, peroxynitrite modified DNA and nitrated proteins can act as neoantigens and lead to the generation of autoantibodies against self-components in autoimmune disorders.