An immuno-DOT diagnostic assay for autoimmune nodopathy.

OBJECTIVES: Autoimmune nodopathy (AN) is a life-threatening peripheral neuropathy mediated by four autoantibodies targeting axoglial cell adhesion molecules at the nodes of Ranvier: Neurofascin-155 (Nfasc155), PanNeurofascin (PanNfasc), Contactin-1 (CNTN1), and Contactin-associated protein 1 (CASPR1). Antibody detection is a strong biomarker for AN diagnosis and treatment monitoring. The aim of this study was to develop an immuno-dot assay (immuno-DOT) compatible with routine implementation in medical laboratories. METHODS: This new approach was compared to standard techniques: indirect immunofluorescence assay, cell-based assay, and ELISA. Sensitivities (Se) and specificities (Sp) were calculated on a cohort composed of 58 patients diagnosed with AN, 50 seronegative patients with chronic inflammatory demyelinating polyradiculoneuropathy, 20 healthy controls, 30 patients with Guillain-Barré syndrome, 20 with monoclonal gammopathy and 20 with Charcot-Marie-Tooth disease. The patients were diagnosed with AN based on compatible electro-clinical arguments and at least two positive standard techniques. RESULTS: Immuno-DOT sensitivities and specificities were Se=91 %, Sp=97 % for anti-Nfasc155; Se=80 %, Sp=94 % for anti-PanNfasc; Se=93 %, Sp=98 % for anti-CNTN1; and Se=87 %, Sp=94 % for anti-CASPR1. Immuno-DOT allowed the diagnosis within 3 h and the accurate follow-up of the immune reactivity and isotype, and dot intensity correlated with antibody titers following treatments. A longitudinal study indicated that immuno-DOT yielded reliable results even after six months of storage at -20 °C. CONCLUSIONS: The diagnostic performance of immuno-DOT was satisfactory and compatible with routine implementation in medical laboratories.

Prevalence of anti-neutrophil cytoplasmic antibody-associated vasculitis in the south of France, using the capture-recapture method.

OBJECTIVES: This study aimed to estimate the prevalence of ANCA-associated vasculitis (AAV), ie granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA), in Southern France in 2018, and evaluate differences among Europeans and non-Europeans. METHODS: This population-based, cross-sectional study used four sources (hospitals, community-based physicians, laboratories, National Health Insurance) to identify adults ≥ 15 years diagnosed with GPA, MPA or EGPA, living in Hérault and Gard in 2018. Cases were defined using the ACR/EULAR classification criteria, and if necessary, the European Medicines Agency algorithm. Prevalence estimates were standardised to the world population and capture-recapture analysis was used to assess the comprehensiveness of the estimation. The influence of geographical origin was evaluated. RESULTS: 202 patients were selected, with 86 cases of GPA (42.6%), 85 cases of MPA (42.1%), and 31 cases of EGPA (15.3%). The standardised prevalence estimates per million inhabitants for 2018 were: 103 (95%CI 84 - 125) for AAV, 48 (95%CI 35 - 64) for GPA, 39 (95%CI 28 - 53) for MPA and 16 (95%CI 9 - 26) for EGPA, 36 (95%CI 25 - 50) for anti-PR3 positive AAV, 46 (95%CI 34 - 61) for anti-MPO positive AAV, and 16 (95%CI 9 - 26) for ANCA-negative AAV. The global estimation of comprehensiveness by capture-recapture analysis was 80.5%. The number of AAV cases was higher for non-European residents (P=0.001), particularly for MPA (P<0.0001). CONCLUSION: We provide a new estimate of AAV prevalence in France and show a higher prevalence of MPA in non-European patients.

Immune-mediated diseases involving central and peripheral nervous systems.

BACKGROUND AND PURPOSE: In addition to combined central and peripheral demyelination, other immune diseases could involve both the central nervous system (CNS) and peripheral nervous system (PNS). METHODS: To identify immune-mediated diseases responsible for symptomatic combined central/peripheral nervous system involvement (ICCPs), we conducted a multicentric retrospective study and assessed clinical, electrophysiological, and radiological features of patients fulfilling our ICCP criteria. RESULTS: Thirty patients (20 males) were included and followed during a median of 79.5 months (interquartile range [IQR] = 43-145). The median age at onset was 51.5 years (IQR = 39-58). Patients were assigned to one of four groups: (i) monophasic disease with concomitant CNS/PNS involvement including anti-GQ1b syndrome (acute polyradiculoneuropathy + rhombencephalitis, n = 2), checkpoint inhibitor-related toxicities (acute polyradiculoneuropathy + encephalitis, n = 3), and anti-glial fibrillary acidic protein astrocytopathy (subacute polyradiculoneuropathy and meningoencephalomyelitis with linear gadolinium enhancements, n = 2); (ii) chronic course with concomitant CNS/PNS involvement including paraneoplastic syndromes (ganglionopathy/peripheral hyperexcitability + limbic encephalitis, n = 4); (iii) chronic course with sequential CNS/PNS involvement including POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome (polyradiculoneuropathy + strokes, n = 2), histiocytosis (polyradiculoneuropathy + lepto-/pachymeningitis, n = 1), and systemic vasculitis (multineuropathy + CNS vasculitis/pachymeningitis, n = 2); and (iv) chronic course with concomitant or sequential CNS/PNS involvement including combined central and peripheral demyelination (polyradiculoneuropathy + CNS demyelinating lesions, n = 10) and connective tissue diseases (ganglionopathy/radiculopathy/multineuropathy + limbic encephalitis/transverse myelitis/stroke, n = 4). CONCLUSIONS: We diagnosed nine ICCPs. The timing of central and peripheral manifestations and the disease course help determine the underlying immune disease. When antibody against neuroglial antigen is identified, CNS and PNS involvement is systematically concomitant, suggesting a common CNS/PNS antigen and a simultaneous disruption of blood-nerve and blood-brain barriers.

Contactin-1 is a novel target antigen in membranous nephropathy associated with chronic inflammatory demyelinating polyneuropathy.

Primary membranous nephropathy (MN) is an autoimmune glomerular disease in which autoantibodies are directed against podocyte proteins. In about 80% of cases the main targeted antigen is the phospholipase A2 receptor 1 (PLA2R1). Anti-PLA2R1 antibodies are mainly immunoglobulin G type 4 (IgG4). However, the antigenic target remains to be defined in 20% of cases. MN can be associated with chronic inflammatory demyelinating polyneuropathy, an autoimmune disease of the peripheral nervous system where a common antigenic target has yet to be identified. To ascertain a possible novel target antigen, we analyzed kidney biopsies from five patients positive for anti-contactin 1 antibodies and presenting with MN combined with chronic inflammatory demyelinating polyneuropathy. Eluted IgG from biopsy sections against contactin 1 and nerve tissue were screened. Western blot revealed contactin 1 expression in normal kidney glomeruli. Confocal microscopic analysis showed the presence and colocalization of contactin 1 and IgG4 on the glomerular basement membrane of these patients. Glomerular contactin 1 was absent in patients with anti-PLA2R1-associated MN or membranous lupus nephritis or a healthy control. The eluted IgG from contactin 1-positive biopsy sections but not the IgG eluted from patients with PLA2R1 MN bound contactin 1 with the main eluted subclass IgG4. Eluted IgG could bind paranodal tissue (myelinated axon) and colocalized with commercial anti-contactin 1 antibody. Thus, contactin 1 is a novel common antigenic target in MN associated with chronic inflammatory demyelinating polyneuropathy. However, the precise pathophysiology remains to be elucidated.

CD8+ T-cell encephalitis mimicking PRES in AIDS: a case report.

BACKGROUND: Diverse mechanisms including infections, autoimmune inflammatory reactions, neoplasms, and degeneration are involved in the central nervous system in cases of acquired immune deficiency syndrome. In such cases, it is difficult to determine the precise pathogenesis by radiological examination and laboratory testing. CASE PRESENTATION: We report a 37-year-old Japanese woman who had untreated hypertension and gender identity disorder and had been taking testosterone injections since she was 19 years old. She developed a headache and visual field deficits together with elevated blood pressure. According to radiological findings, she was initially suspected as having posterior reversible encephalopathy syndrome in the right parieto-occipital lobe with reversible cerebral vasoconstriction syndrome. Human immunodeficiency virus antibody was positive and the CD4+ T-lymphocyte count was 140 cells/µl. Therefore, antiretroviral therapy was started. Antiretroviral therapy suppressed the activity of acquired immune deficiency syndrome but worsened her visual symptoms and expanding radiological lesions. Brain biopsy led to the diagnosis of CD8+ encephalitis, and she also fulfilled the diagnosis of paradoxical immune reconstitution inflammatory syndrome. Corticosteroid therapy alleviated her symptoms. CONCLUSIONS: This is a rare case of CD8+ encephalitis, with an exacerbation owing to paradoxical immune reconstitution inflammatory syndrome after antiretroviral therapy, which radiologically mimicked posterior reversible encephalopathy syndrome. Corticosteroid therapy was effective; thus, it is important to provide a pathological diagnosis in such cases.

Progressive Multifocal Leukoencephalopathy in Primary Immunodeficiencies.

PURPOSE: Progressive multifocal leukoencephalopathy (PML) is a rare but severe demyelinating disease caused by the polyomavirus JC (JCV) in immunocompromised patients. We report a series of patients with primary immune deficiencies (PIDs) who developed PML. METHODS: Retrospective observational study including PID patients with PML. Clinical, immunological, imaging features, and outcome are provided for each patient. RESULTS: Eleven unrelated patients with PIDs developed PML. PIDs were characterized by a wide range of syndromic or genetically defined defects, mostly with combined B and T cell impairment. Genetic diagnosis was made in 7 patients. Before the development of PML, 10 patients had recurrent infections, 7 had autoimmune and/or inflammatory manifestations, and 3 had a history of malignancies. Immunologic investigations showed CD4+ lymphopenia (median 265, range 50-344) in all cases. Six patients received immunosuppressive therapy in the year before PML onset, including prolonged steroid therapy in 3 cases, rituximab in 5 cases, anti-TNF-α therapy, and azathioprine in 1 case each. Despite various treatments, all but 1 patient died after a median of 8 months following PML diagnosis. CONCLUSION: PML is a rare but fatal complication of PIDs. Many cases are secondary to immunosuppressive therapy warranting careful evaluation before initiation subsequent immunosuppression during PIDs.

CLIPPERS and its mimics: evaluation of new criteria for the diagnosis of CLIPPERS.

OBJECTIVE: To evaluate the accuracy of the recently proposed diagnostic criteria for chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS). METHODS: We enrolled 42 patients with hindbrain punctate and/or linear enhancements (<3 mm in diameter) and tested the CLIPPERS criteria. RESULTS: After a median follow-up of 50 months (IQR 25-82), 13 out of 42 patients were CLIPPERS-mimics: systemic and central nervous system lymphomas (n=7), primary central nervous system angiitis (n=4) and autoimmune gliopathies (n=2). The sensitivity and specificity of the CLIPPERS criteria were 93% and 69%, respectively. Nodular enhancement ( ≥ 3 mm in diameter), considered as a red flag in CLIPPERS criteria, was present in 4 out of 13 CLIPPERS-mimics but also in 2 out of 29 patients with CLIPPERS, explaining the lack of sensitivity. Four out of 13 CLIPPERS-mimics who initially met the CLIPPERS criteria displayed red flags at the second attack with a median time of 5.5 months (min 3, max 18), explaining the lack of specificity. One of these four patients had antimyelin oligodendrocyte glycoprotein antibodies, and the three remaining patients relapsed despite a daily dose of prednisone/prednisolone ≥ 30 mg and a biopsy targeting atypical enhancing lesions revealed a lymphoma. CONCLUSIONS: Our study highlights that (1) nodular enhancement should be considered more as an unusual finding than a red flag excluding the diagnosis of CLIPPERS; (2) red flags may occur up to 18 months after disease onset; (3) as opposed to CLIPPERS-mimics, no relapse occurs when the daily dose of prednisone/prednisolone is ≥ 30 mg; and (4) brain biopsy should target an atypical enhancing lesion when non-invasive investigations remain inconclusive.

Inflammatory facioscapulohumeral muscular dystrophy type 2 in 18p deletion syndrome.

Facioscapulohumeral muscular dystrophy (FSHD) has been shown to be related to genetic and epigenetic derepression of DUX4 (mapping to chromosome 4), a gene located within a repeat array of D4Z4 sequences of polymorphic length. FSHD type 1 (FSHD1) is associated with pathogenic D4Z4 repeat array contraction, while FSHD type 2 (FSHD2) is associated with SMCHD1 variants (a chromatin modifier gene that maps to the short arm of chromosome 18). Both FSHD types require permissive polyadenylation signal (4qA) downstream of the D4Z4 array.

Autoantibodies to nodal isoforms of neurofascin in chronic inflammatory demyelinating polyneuropathy.

Chronic inflammatory demyelination polyneuropathy is a heterogeneous and treatable immune-mediated disorder that lacks biomarkers to support diagnosis. Recent evidence indicates that paranodal proteins (contactin 1, contactin-associated protein 1, and neurofascin-155) are the targets of autoantibodies in subsets of patients showing distinct clinical presentations. Here, we identified neurofascin-186 and neurofascin-140 as the main targets of autoantibodies in five patients presenting IgG reactivity against the nodes of Ranvier. Four patients displayed predominantly IgG4 antibodies, and one patient presented IgG3 antibodies that activated the complement pathway in vitro. These patients present distinct clinical features compared to those with anti-neurofascin-155 IgG4. Most patients had a severe phenotype associated with conduction block or decreased distal motor amplitude. Four patients had a subacute-onset and sensory ataxia. Two patients presented with nephrotic syndromes and one patient with an IgG4-related retroperitoneal fibrosis. Intravenous immunoglobulin and corticosteroids were effective in three patients, and one patient remitted following rituximab treatment. Clinical remission was associated with autoantibody depletion and with recovery of conduction block and distal motor amplitude suggesting a nodo-paranodopathy. Our data demonstrate that the pathogenic mechanisms responsible for chronic inflammatory demyelination polyneuropathy are broad and may include dysfunctions at the nodes of Ranvier in a subgroup of patients.

Punctate and curvilinear gadolinium enhancing lesions in the brain: a practical approach.

INTRODUCTION: Cerebral punctate and curvilinear gadolinium enhancements (PCGE) correspond to opacification of small vessel lumen or its perivascular areas in case of blood-brain barrier (BBB) disruption. We will discuss the possible causes of intra-parenchymal central nervous system PCGE. METHODS: Our review is based on French database including patients presenting with central nervous system PCGE and literature search using PubMed database with the following keywords: punctate enhancement, linear enhancement, and curvilinear enhancement. Disorders which displayed linear leptomeningeal or periventricular enhancements without intra-parenchymal PCGE are excluded of this review. RESULTS: Among our 39 patients with PCGE, 16 different diagnoses were established. After combining our PCGE causes with those described in the literature, we propose a practical approach. Besides physiologic post-contrast enhancement of small vessels, three pathologic conditions may exhibit PCGE: (1) small collateral artery network seen in Moyamoya syndrome, (2) small veins congestions related to developmental or acquired venous outflow disturbance, and (3) disorders causing small vessels BBB disruption indicated by T2 and FLAIR hyperintensities in the corresponding areas of PCGE. Disruption of the BBB could be caused by a direct injury of the endothelial cell, as in posterior reversible encephalopathy syndrome, Susac syndrome, and radiochemotherapy-induced injuries, or by an angiocentric cellular infiltrate, as in inflammatory disorders, demyelinating diseases, host immune responses fighting against infections, prelymphoma states, lymphoma, and in CLIPPERS. CONCLUSION: PCGE may conceal several causes, including physiological and pathological conditions. Nevertheless, a practical approach could improve its management and limit the indications of brain biopsy to very specific situations.

Proximal conduction block in the pharyngeal-cervical-brachial variant of Guillain-Barré syndrome.

INTRODUCTION: Conduction block (CB) has been included in the Rajabally criteria for axonal Guillain-Barré syndrome (GBS). Because the nerve roots may be affected early in GBS, detection of proximal CB by the triple stimulation technique (TST) can be useful. METHODS: We describe TST findings in 2 patients who presented with the pharyngeal-cervical-brachial (PCB) variant of axonal GBS. RESULTS: In the first patient, although conventional nerve conduction studies (NCS) did not fit electrodiagnostic criteria for axonal GBS, the TST detected proximal CB in the median and ulnar nerves. In the second patient, NCS fulfilled criteria for axonal GBS, and the TST detected proximal CB in the median nerve. After plasmapheresis, NCS and TST findings were normalized, suggesting reversible conduction failure rather than demyelinating CB. CONCLUSION: The TST may be useful for diagnosis of PCB when NCS remain inconclusive. The technique provides additional clues for classifying PCB into the acute nodo-paranodopathies.

An MRI review of acquired corpus callosum lesions.

Lesions of the corpus callosum (CC) are seen in a multitude of disorders including vascular diseases, metabolic disorders, tumours, demyelinating diseases, trauma and infections. In some diseases, CC involvement is typical and sometimes isolated, while in other diseases CC lesions are seen only occasionally in the presence of other typical extra-callosal abnormalities. In this review, we will mainly discuss the MRI characteristics of acquired lesions involving the CC. Identification of the origin of the CC lesion depends on the exact localisation of the lesion(s) inside the CC, presence of other lesions seen outside the CC, signal changes on different MRI sequences, evolution over time of the radiological abnormalities, history and clinical state of the patient, and other radiological and non-radiological examinations.

Sensory chronic inflammatory demyelinating polyneuropathy: an under-recognized entity?

INTRODUCTION: Sensory chronic inflammatory demyelinating polyneuropathy (CIDP) can be difficult to diagnose. METHODS: We report 22 patients with chronic sensory polyneuropathy with ≥1 clinical sign atypical for chronic idiopathic axonal polyneuropathy (CIAP) but no electrodiagnostic criteria for CIDP. RESULTS: Clinical signs atypical for CIAP were: sensory ataxia (59%), generalized areflexia (36%), cranial nerve involvement (32%), rapid upper limb involvement (40%), and age at onset ≤55 years (50%). Additional features were: normal sensory nerve action potentials (36%), abnormal radial/normal sural pattern (23%), abnormal somatosensory evoked potentials (SSEPs) (100%), elevated cerebrospinal fluid (CSF) protein (73%), and demyelinating features in 5/7 nerve biopsies. Over 90% of patients responded to immunotherapy. We conclude that all patients had sensory CIDP. CONCLUSIONS: Sensory CIDP patients can be misdiagnosed as having CIAP. If atypical clinical/electrophysiologic features are present, we recommend performing SSEPs and CSF examination. Nerve biopsy should be restricted to disabled patients if other examinations are inconclusive.

Effect of monovalency on anti-contactin-1 IgG4.

Introduction: Autoimmune nodopathies (AN) have been diagnosed in a subset of patients fulfilling criteria for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who display no or poor response to intravenous immunoglobulins. Biomarkers of AN are autoantibodies, mainly IgG4, directed against the ternary paranodal complex composed by neurofascin-155, contactin-1 (CNTN1), and Contactin-associated-protein-1 (CASPR1) or against the nodal isoforms of neurofascin. IgG4 can undergo a Fab-arm exchange (FAE) which results in functionally monovalent antibody. This phenomenon differentially affects the pathogenicity of IgG4 depending on the target of autoantibodies. Here, we have evaluated this issue by examining the impact of valency on anti-CNTN1 IgG4 which induces paranodal destruction through a function blocking activity. Methods: Sera were obtained from 20 patients with AN associated with anti-CNTN1 antibodies. The proportion of monospecific/bispecific anti-CNTN1 antibodies was estimated in each patient by ELISA by examining the ability of serum antibodies to cross-link untagged CNTN1 with biotinylated CNTN1. To determine the impact of monovalency, anti-CNTN1 IgG4 were enzymatically digested into monovalent Fab and tested in vitro on cell aggregation assay. Also, intraneural injections were performed to determine whether monovalent Fab and native IgG4 may penetrate paranode, and antibody infiltration was monitored 1- and 3-days post injection. Results and discussion: We found that the percentage of monospecific antibodies were lower than 5% in 14 out of 20 patients (70%), suggesting that IgG4 have undergone extensive FAE in situ. The levels of monospecific antibodies correlated with the titers of anti-CNTN1 antibodies. However, no correlation was found with clinical severity, and patients with low or high percentage of monospecific antibodies similarly showed a severe phenotype. Native anti-CNTN1 IgG4 were shown to inhibit the interaction between cells expressing CNTN1/CASPR1 and cells expressing neurofascin-155 using an in vitro aggregation assay. Similarly, monovalent Fab significantly inhibited the interaction between CNTN1/CASPR1 and neurofascin-155. Intraneural injections of Fab and native anti-CNTN1 IgG4 indicated that both mono- and bivalent anti-CNTN1 IgG4 potently penetrated the paranodal regions and completely invaded this region by day 3. Altogether, these data indicate anti-CNTN1 IgG4 are mostly bispecific in patients, and that functionally monovalent anti-CNTN1 antibodies have the pathogenic potency to alter paranode.

Frontal Intermittent Rhythmic Delta Activity Is a Useful Diagnostic Tool of Neurotoxicity After CAR T-Cell Infusion.

BACKGROUND AND OBJECTIVES: Chimeric antigen receptor (CAR) T-cell therapies have dramatically improved the prognosis of patients with relapsed or refractory hematologic malignancies; however, cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (ICANS) occur in ∼100 and 50% of patients, respectively. This study aimed to determine whether EEG patterns may be considered as diagnostic tools for ICANS. METHODS: Patients who received CAR T-cell therapy at Montpellier University Hospital between September 2020 and July 2021 were prospectively enrolled. Neurologic signs/symptoms and laboratory parameters were monitored daily for 14 days after CAR T-cell infusion. EEG and brain MRI were performed between day 6 and 8 after CAR T-cell infusion. EEG was performed again on the day of ICANS occurrence, if outside this time window. All collected data were compared between patients with and without ICANS. RESULTS: Thirty-eight consecutive patients were enrolled (14 women; median age: 65 years, interquartile range: [55-74]). ICANS was observed in 17 of 38 patients (44%) after a median time of 6 days after CAR T-cell infusion (4-8). The median ICANS grade was 2 (1-3). Higher C-reactive protein peak (146 mg/L [86-256], p = 0.004) at day 4 (3-6), lower natremia (131 mmol/L [129-132], p = 0.005) at day 5 (3-6), and frontal intermittent rhythmic delta activity (FIRDA, p < 0.001) on EEG between days 6 and 8 after infusion were correlated with ICANS occurrence. FIRDA was only observed in patients with ICANS (N = 15/17, sensitivity of 88%) and disappeared after ICANS resolution, usually after steroid therapy. Except for hyponatremia, no other toxic/metabolic marker was associated with FIRDA (p = 0.002). The plasma concentration of copeptin, a surrogate marker of antidiuretic hormone secretion, assessed at day 7 after infusion, was significantly higher in patients with (N = 8) than without (N = 6) ICANS (p = 0.043). DISCUSSION: FIRDA is a reliable diagnostic tool for ICANS, with a sensitivity of 88% and a negative predictive value of 100%. Moreover, as this EEG pattern disappeared concomitantly with ICANS resolution, FIRDA could be used to monitor neurotoxicity. Finally, our study suggests a pathogenic pathway that starts with increased C-reactive protein, followed by hyponatremia and eventually ICANS and FIRDA. More studies are required to confirm our results. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that FIRDA on spot EEG accurately distinguishes patients with ICANS compared with those without after CAR T-cell therapy for hematologic malignancy.