Intracranial calcifications simulating Aicardi-Goutières syndrome in PARS2-related mitochondrial disease.

PARS2 encodes an aminoacyl-tRNA synthetase that catalyzes the ligation of proline to mitochondrial prolyl-tRNA molecules. Diseases associated with PARS2 primarily affect the central nervous system, causing early infantile developmental epileptic encephalopathies (EIDEE; DEE75; MIM #618437) with infantile-onset neurodegeneration. Dilated cardiomyopathy has also been reported in the affected individuals. About 10 individuals to date have been described with pathogenic biallelic variants in PARS2. While many of the reported individuals succumbed to the disease in the first two decades of life, autopsy findings have not yet been reported. Here, we describe neuropathological findings in a deceased male with evidence of intracranial calcifications in the basal ganglia, thalamus, cerebellum, and white matter, similar to Aicardi-Goutières syndrome. This report describes detailed autopsy findings in a child with PARS2-related mitochondrial disease and provides plausible evidence that intracranial calcifications may be a previously unrecognized feature of this disorder.

Generation of three induced pluripotent stem cell lines from individuals with Aicardi-Goutières syndrome caused by a c.3019G>A (p.G1007R) autosomal dominant pathogenic variant in ADAR1.

Mutations in Adenosine deaminase acting on RNA 1 (ADAR1) gene encoding RNA editing enzyme ADAR1 results in the neuroinflammatory leukodystrophy Aicardi Goutières Syndrome (AGS). AGS is an early onset leukoencephalopathy with an exacerbated interferon response leading to neurological regression with intellectual disability, spasticity, and motor deficits. We have generated three induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells (PBMCs) of individuals with ADAR1G1007R mutation. The generated iPSCs were investigated to confirm a normal karyotype, pluripotency, and trilineage differentiation potential. The reprogrammed iPSCs will allow us to model AGS, dissect the cellular mechanisms and testing different treatment targets.

Pathological findings in autoimmune encephalitis autopsy specimens from cases of suspected prion disease.

OBJECTIVE: The underlying pathology of autoimmune encephalitis is not well characterized due to the limited opportunities to study tissue specimens. Autopsy specimens available at prion surveillance centers from patients with suspected Creutzfeldt-Jakob disease offer a unique opportunity to study the pathology of autoimmune encephalitis. Our objective was to describe pathological findings of autoimmune encephalitis specimens submitted to the U.S. National Prion Disease Pathology Surveillance Center. METHODS: Pathology reports were obtained from the National Prion Center. Specimens negative for prion disease were screened for inflammatory pathology and those suggestive of autoimmune encephalitis were analyzed. Cases identified on autopsy were compared to institutional cases with fatal seronegative autoimmune encephalitis and available brain biopsy. RESULTS: Between 1998 and 2022, 7934 specimens were evaluated of which 2998 (38%) were negative for prion protein. Querying the database for alternative diagnoses of encephalitis/encephalopathy yielded 43 cases that were screened by an experienced neuropathologist yielding 14 (0.5%) cases consistent with autoimmune encephalitis. Most specimens showed diffuse inflammation involving the limbic system (86%), basal ganglia (86%), cortex (71%), diencephalon (71%), and in some cases the brainstem (43%) and cerebellum (43%). Lymphocytic inflammatory infiltrate was predominantly perivascular with parenchymal extension in 64%. Microglial activation/nodules were seen in 64% of cases. Neuronal loss was present only in 50%. Pathological findings were identical to biopsy specimens from our institutional cohort. DISCUSSION: Seronegative AE may have consistent pathology with diffuse or multifocal perivascular inflammation and microglial activation. Half the patients do not have neuronal loss suggesting a potential for neurological recovery. These findings are preliminary and require further confirmation.

[Establishment of induced pluripotent stem cell model of Aicardi-Goutières Syndrome mutated in TREX1].

To establish and identify induced pluripotent stem cells (iPSCs) derived from patients with Aicardi-Goutières syndrome (AGS) with TREX1 gene 667G>A mutation, and obtain a specific induced pluripotent stem cell model for Aicardi-Goutières syndrome (AGS-iPSCs). A 3-year-old male child with Aicardi-Goutieres syndrome was admitted to Zhongshan People's Hospital in December 2020. After obtaining the informed consent of the patient's family members, 5 ml peripheral blood samples from the patient were collected, and mononuclear cells were isolated. Then,the peripheral blood mononuclear cells(PBMCs) were transduced with OCT3/4, SOX2, c-Myc and Klf4 by using Sendai virus, and PBMCs were reprogrammed into iPSCs. The pluripotency and differentiation ability of the cells were identified by cellular morphological analysis, real-time PCR, alkaline phosphatase staining (AP), immunofluorescence, teratoma formation experiments in mice. The results showed that the induced pluripotent stem cell line of Aicardi-Goutieres syndrome was successfully constructed and showed typical embryonic stem-like morphology after stable passage, RT-PCR showed mRNA expression of stem cell markers, AP staining was positive, OCT4, SOX2, NANOG, SSEA4, TRA-1-81 and TRA-1-60 pluripotency marker proteins were strongly expressed. In vivo teratoma formation experiments showed that iPSCs differentiate into the ectoderm (neural tube like tissue), mesoderm (vascular wall tissue) and endoderm (glandular tissue). Karyotype analysis also confirmed that iPSCs still maintained the original karyotype (46, XY). In conclusion, induced pluripotent stem cell line for Aicardi-Goutières syndrome was successfully established using Sendai virus, which provided an important model platform for studying the pathogenesis of the disease and for drug screening.

A case of Aicardi-Goutières syndrome caused by TREX1 gene mutation.

Aicardi-Goutières syndrome (AGS) is a rare genetic disorder involving the central nervous system and autoimmune abnormalities, leading to severe intellectual and physical disability with poor prognosis. AGS has a phenotype similar to intrauterine viral infection, which often leads to delays in genetic counseling. In this study, we report a case with a prenatal diagnosis of AGS. The first fetal ultrasound detected bilateral lateral ventricle cystic structures, and fetal MRI was performed to identify other signs. The right parietal lobe signal showed cerebral white matter abnormalities, and fetal brain development level was lower than that of normal fetuses of the same gestational age. Whole-exome sequencing revealed that the fetus carried the TREX1:NM_033629.6:exon2:c.294dup:p. C99Mfs*3 variant, suggesting that the c.294dup mutation of the TREX1 gene was the pathogenic mutation site, and the final comprehensive diagnosis was AGS1. In this article, we also reviewed the previous literature for possible phenotypes in the fetus and found that microcephaly and intrauterine growth retardation may be the first and most important markers of the intrauterine phenotype of AGS.

A novel pathogenic variant p.Asp797Val in IFIH1 in a Japanese boy with overlapping Singleton-Merten syndrome and Aicardi-Goutières syndrome.

Pathogenic-activating variants of interferon induced with Helicase C domain 1 (IFIH1) cause Singleton-Merten (S-M) syndrome, which accompanies acro-osteolysis, loss of permanent teeth, and aortic calcification, as well as causing Aicardi-Goutières (A-G) syndrome, which shows progressive encephalopathy, spastic paraplegia, and calcification of basal ganglia. Recently, patients with overlapping syndromes presenting with features of S-M syndrome and A-G syndrome were reported. However, progression of clinical features of this condition has not been fully understood. We report a Japanese boy with a novel pathogenic IFIH1 variant who presented with clinical features of S-M syndrome and A-G syndrome.

Autoimmune glial fibrillary acidic protein astrocytopathy resembling isolated central nervous system lymphomatoid granulomatosis.

We report two patients with meningoencephalomyelitis without evidence of extra central nervous system (CNS) involvement. Brain MRI showed linear perivascular radial gadolinium enhancement patterns and spinal cord MRI showed longitudinal extensive T2-hyperintensity lesions. Pathological findings from brain biopsies were angiocentric T-cell predominant lymphoid infiltrates that lacked Epstein-Barr virus-positive atypical B cells. The patients were initially suspected to have isolated CNS-lymphomatoid granulomatosis (LYG). Thereafter, glial fibrillary acidic protein (GFAP)-immunoglobulin G were detected in their cerebrospinal fluid. This finding suggested autoimmune GFAP astrocytopathy. We speculate there is a link between isolated CNS-LYG and autoimmune GFAP astrocytopathy.

Autopsy Case of Meningoencephalomyelitis Associated With Glial Fibrillary Acidic Protein Antibody.

BACKGROUND AND OBJECTIVES: To describe the autopsy findings and neuropathologic evaluation of autoimmune meningoencephalomyelitis associated with glial fibrillary acidic protein (GFAP) antibody. METHODS: We reviewed the clinical course, imaging, laboratory, and autopsy findings of a patient with autoimmune meningoencephalomyelitis associated with GFAP antibody who had a refractory course to multiple immunosuppressive therapies. RESULTS: The patient was a 70-year-old man who was diagnosed as GFAP antibody-associated autoimmune meningoencephalomyelitis. MRI of the head showed linear perivascular enhancement in the midbrain and the basal ganglia. Despite treatment with high-dose corticosteroids, plasma exchange, IV immunoglobulins, and cyclophosphamide, he died with devastating neurologic complications. Autopsy revealed a coexistent neuroendocrine tumor in the small intestine and diffuse inflammation in the brain parenchyma, perivascular spaces, and leptomeninges, with predominant T-cells, macrophages, and activated microglia. B-cells and plasma cells were absent. There was no astrocyte involvement with change in GFAP immunostaining. DISCUSSION: This case illustrates autoimmune meningoencephalomyelitis associated with GFAP antibody in the CSF and coexistent neuroendocrine tumor. The autopsy findings were nonspecific and did not demonstrate astrocyte involvement. Further accumulation of cases is warranted to delineate the utility and pathogenic significance of the GFAP autoantibody.

Protein kinase R and the integrated stress response drive immunopathology caused by mutations in the RNA deaminase ADAR1.

The RNA deaminase ADAR1 is an essential negative regulator of the RNA sensor MDA5, and loss of ADAR1 function triggers inappropriate activation of MDA5 by self-RNAs. Mutations in ADAR, the gene that encodes ADAR1, cause human immune diseases, including Aicardi-Goutières syndrome (AGS). However, the mechanisms of MDA5-dependent disease pathogenesis in vivo remain unknown. Here we generated mice with a single amino acid change in ADAR1 that models the most common human ADAR AGS mutation. These Adar mutant mice developed lethal disease that required MDA5, the RIG-I-like receptor LGP2, type I interferons, and the eIF2α kinase PKR. A small-molecule inhibitor of the integrated stress response (ISR) that acts downstream of eIF2α phosphorylation prevented immunopathology and rescued the mice from mortality. These findings place PKR and the ISR as central components of immunopathology in vivo and identify therapeutic targets for treatment of human diseases associated with the ADAR1-MDA5 axis.

Thymoma and Autoimmune Encephalitis: Clinical Manifestations and Antibodies.

OBJECTIVE: To report the clinical, neuroimaging, and antibody associations in patients with autoimmune encephalitis (AE) and thymoma. METHODS: A retrospective cohort study of 43 patients was conducted. Antibody determination and immunoprecipitation to characterize novel antigens were performed using reported techniques. RESULTS: Patients' median age was 52 years (range: 23-88 years). Forty (93%) had neuronal surface antibodies: gamma-aminobutyric acid receptor A (GABAAR) (15), amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) (13), contactin-associated protein-like 2 (CASPR2) (4), leucine-rich, glioma inactivated 1 (LGI1) (3), glycine receptor (GlyR) (3), and unknown antigens (2). Concurrent antibodies against intracellular antigens occurred in 13 (30%; 9 anti-collapsin response mediator protein 5 [CRMP5]) and were more frequent in anti-AMPAR encephalitis (54% vs 20%; p = 0.037). The most common clinical presentation was encephalitis with multiple T2/fluid-attenuated inversion recovery hyperintense lesions in 23 (53%) patients (15 GABAAR, 5 AMPAR, and 1 unknown neuropil antibody), followed by encephalitis with peripheral nerve hyperexcitability in 7 (16%; 4 CASPR2, 2 LGI1, and 1 unknown antibody), limbic encephalitis in 6 (14%; 4 AMPAR, 1 LGI1, and 1 antibody negative), progressive encephalomyelitis with rigidity and myoclonus in 4 (9%; 3 GlyR and 1 AMPAR antibodies), and encephalitis with normal MRI in 3 (7%; AMPAR antibodies). Anti-GABAAR encephalitis was more prevalent in Japanese patients compared with Caucasians and other ethnicities (61% vs 16%; p = 0.003). In anti-AMPAR encephalitis, 3/4 patients with poor and 0/6 with good outcome had concurrent CRMP5 antibodies (p = 0.033). Immunoprecipitation studies identified metabotropic glutamate receptor 3 antibodies that were additionally found in 5 patients (3 with and 2 without encephalitis). CONCLUSIONS: AE in patients with thymoma include several clinical-radiologic syndromes that vary according to the associated antibodies. Anti-GABAAR encephalitis was the most frequent AE and occurred more frequently in Japanese patients.

Severe diarrhea in a 10-year-old girl with Aicardi-Goutières syndrome due to IFIH1 gene mutation.

Interferon-induced with helicase C domain 1 (IFIH1) is a cytosolic sensor of dsRNA that induces an anti-viral Type I interferon (IFN) state. A gain-of-function mutation in IFIH1 can cause increased Type I IFN activity and is clinically associated with Aicardi-Goutières syndrome (AGS). AGS is a multisystem disease, characterized as an early-onset progressive encephalopathy with basal ganglia calcification and systemic lupus erythematosus-like features. Gastrointestinal manifestation is rare in AGS patients. We described a 10-year-old female patient with a heterozygous IFIH1 gene mutation who presented with gastrointestinal colitis, cystitis and very severe diarrhea as initial major manifestations of AGS. Proteinuria with high titer of antinuclear antibody and anti-double-stranded DNA was found in this patient. She also had growth retardation and a history of seizures (about two episodes each year) but without attacks until 7 years old. Serum cytokines detected by flow cytometry indicated extremely high level of interleukin 6 (1970.1 pg/ml) and IFN-α (204.1 pg/ml). A contrast-enhanced CT scan of the whole abdomen and an intestinal hydro-MRI indicated that the walls of her stomach, small bowel, colon, and bladder were in various degrees of edema and thickened states. Whole exome sequencing analysis indicated that she harbors an IFIH1 heterozygous mutation (c.2336G > A (p.R779H)) in both blood and intestinal samples. Abundant inflammatory cells infiltration into the intestinal epithelium was observed by immunohistochemical staining. Positive staining of caspase 4 and caspase 5 suggested that the signaling pathway of pyroptosis was involved in the mechanism of intestinal inflammation in AGS. Diarrhea was significantly improved after steroids and intravenous immunoglobulin treatments. Gastrointestinal colitis and cystitis can be rare manifestations of AGS with IFIH1 mutation. Caspase and its related inflammasome pathway may involve in the pathogenesis of AGS.

Autoimmune Global Amnesia as Manifestation of AMPAR Encephalitis and Neuropathologic Findings.

OBJECTIVE: To report an unusual clinical phenotype of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and describe associated neuropathologic findings. METHODS: We retrospectively investigated 3 AMPAR encephalitis patients with autoimmune global hippocampal amnesia using comprehensive cognitive and neuropsychologic assessment, antibody testing by in-house tissue-based and cell-based assays, and neuropathologic analysis of brain autopsy tissue including histology and immunohistochemistry. RESULTS: Three patients presented with acute-to-subacute global amnesia without affection of cognitive performance, attention, concentration, or verbal function. None of the patients had epileptic seizures, change of behavior, personality changes, or psychiatric symptoms. The MRI was normal in 1 patient and showed increased fluid-attenuated inversion recovery/T2 signal in the hippocampus in the other 2 patients. Two patients showed complete remission after immunotherapy. The one patient who did not improve had an underlying adenocarcinoma of the lung and died 3.5 months after disease onset because of tumor progression. Neuropathologic analysis of the brain autopsy revealed unilateral hippocampal sclerosis accompanied by mild inflammatory infiltrates, predominantly composed of T lymphocytes, and decrease of AMPAR immunoreactivity. CONCLUSION: AMPAR antibodies usually associate with limbic encephalitis but may also present with immune responsive, acute-to-subacute, isolated hippocampal dysfunction without overt inflammatory CSF or MRI changes.

Aicardi-Goutières syndrome-associated gene SAMHD1 preserves genome integrity by preventing R-loop formation at transcription-replication conflict regions.

The comorbid association of autoimmune diseases with cancers has been a major obstacle to successful anti-cancer treatment. Cancer survival rate decreases significantly in patients with preexisting autoimmunity. However, to date, the molecular and cellular profiles of such comorbidities are poorly understood. We used Aicardi-Goutières syndrome (AGS) as a model autoimmune disease and explored the underlying mechanisms of genome instability in AGS-associated-gene-deficient patient cells. We found that R-loops are highly enriched at transcription-replication conflict regions of the genome in fibroblast of patients bearing SAMHD1 mutation, which is the AGS-associated-gene mutation most frequently reported with tumor and malignancies. In SAMHD1-depleted cells, R-loops accumulated with the concomitant activation of DNA damage responses. Removal of R-loops in SAMHD1 deficiency reduced cellular responses to genome instability. Furthermore, downregulation of SAMHD1 expression is associated with various types of cancer and poor survival rate. Our findings suggest that SAMHD1 functions as a tumor suppressor by resolving R-loops, and thus, SAMHD1 and R-loop may be novel diagnostic markers and targets for patient stratification in anti-cancer therapy.

Aicardi-Goutières syndrome-like encephalitis in mutant mice with constitutively active MDA5.

MDA5 is a cytoplasmic sensor of viral RNA, triggering type I interferon (IFN-I) production. Constitutively active MDA5 has been linked to autoimmune diseases such as systemic lupus erythematosus, Singleton-Merten syndrome (SMS) and Aicardi-Goutières syndrome (AGS), a genetically determined inflammatory encephalopathy. However, AGS research is challenging due to the lack of animal models. We previously reported lupus-like nephritis and SMS-like bone abnormalities in adult mice with constitutively active MDA5 (Ifih1G821S/+), and herein demonstrate that these mice also exhibit high lethality and spontaneous encephalitis with high IFN-I production during the early postnatal period. Increases in the number of microglia were observed in MDA5/MAVS signaling- and IFN-I-dependent manners. Furthermore, microglia showed an activated state with an increased phagocytic capability and reduced expression of neurotrophic factors. Although multiple auto-antibodies including lupus-related ones were detected in the sera of the mice as well as AGS patients, Ifih1G821S/+Rag2-/- mice also exhibited up-regulation of IFN-I, astrogliosis and microgliosis, indicating that auto-antibodies or lymphocytes are not required for the development of the encephalitis. The IFN-I signature without lymphocytic infiltration observed in Ifih1G821S/+ mice is a typical feature of AGS. Collectively, our results suggest that the Ifih1G821S/+ mice are a model recapitulating AGS and that microglia are a potential target for AGS therapy.

Contactin-1 autoimmunity: Serologic, neurologic, and pathologic correlates.

OBJECTIVE: To determine serologic characteristics, frequency, phenotype, paraneoplastic associations, and electrodiagnostic and histopathologic features accompanying contactin-1 autoimmunity. METHODS: Archived sera known to produce synaptic tissue-based immunofluorescence patterns were reevaluated, and contactin-1 specificity was confirmed by recombinant protein assays. Screening of 233 chronic/relapsing demyelinating neuropathies for additional cases was performed. RESULTS: We identified 10 contactin-1 IgG seropositive cases. Frequency of contactin-1 immunoglobulin (Ig) G among tested Mayo Clinic chronic/relapsing demyelinating neuropathies was 2%. Sensory predominant presentations (n = 9, 90%), neuropathic pain (n = 6, 60%), and subacute progression (n = 5, 50%) were commonly encountered among contactin-1 neuropathies. Two patients had chronic immune sensory polyradiculopathy-like phenotype at presentation. Electrodiagnostic studies were consistent with demyelination (slowed conduction velocities and/or prolonged distal latencies) without conduction block. Markedly elevated CSF protein (median 222 mg/dL, range 69-960 mg/dL), thickening/gadolinium enhancement of nerve roots (4/5), and subperineural edema on nerve biopsy (4/4) were other characteristic features. Three cases were diagnosed with paraneoplastic demyelinating neuropathies (thymoma, n = 1; breast cancer, n = 1; plasmacytoma, n = 1). Four of the 9 patients treated with IV immunoglobulin demonstrated initial clinical improvement, but the favorable response was sustained in only 1 case (median follow-up, 60 months). Sustained clinical stabilization or improvement was observed among 3 of the 6 cases in whom second-line therapies (rituximab, cyclophosphamide, and azathioprine) were used. CONCLUSION: Contactin-1 IgG has a distinct sensory predominant presentation commonly associated with neuropathic pain, with demyelinating changes on electrophysiologic studies. A paraneoplastic cause should be considered. Testing of contactin-1 IgG among cases with similar presentations may guide immunotherapy selection, especially second-line immunotherapy consideration.

Adenosine-to-inosine RNA editing in the immune system: friend or foe?

Our body expresses sensors to detect pathogens through the recognition of expressed molecules, including nucleic acids, lipids, and proteins, while immune tolerance prevents an overreaction with self and the development of autoimmune disease. Adenosine (A)-to-inosine (I) RNA editing, catalyzed by adenosine deaminases acting on RNA (ADARs), is a post-transcriptional modification that can potentially occur at over 100 million sites in the human genome, mainly in Alu repetitive elements that preferentially form a double-stranded RNA (dsRNA) structure. A-to-I conversion within dsRNA, which may induce a structural change, is required to escape from the host immune system, given that endogenous dsRNAs transcribed from Alu repetitive elements are potentially recognized by melanoma differentiation-associated protein 5 (MDA5) as non-self. Of note, loss-of-function mutations in the ADAR1 gene cause Aicardi-Goutières syndrome, a congenital autoimmune disease characterized by encephalopathy and a type I interferon (IFN) signature. However, the loss of ADAR1 in cancer cells with an IFN signature induces lethality via the activation of protein kinase R in addition to MDA5. This makes cells more sensitive to immunotherapy, highlighting the opposing immune status of autoimmune diseases (overreaction) and cancer (tolerance). In this review, we provide an overview of insights into two opposing aspects of RNA editing that functions as a modulator of the immune system in autoimmune diseases and cancer.

Generation of three isogenic induced Pluripotent Stem Cell lines (iPSCs) from fibroblasts of a patient with Aicardi Goutières Syndrome carrying a c.2471G>A dominant mutation in IFIH1 gene.

Aicardi-Goutières syndrome (AGS) is an early-onset monogenic encephalopathy characterized by intracranial calcification, leukodystrophy and cerebrospinal fluid lymphocytosis. To date, seven genes have been related to AGS. Among these, IFIH1 encodes for MDA5, a cytosolic double-stranded RNA receptor, and is responsible for AGS type 7. We generated three isogenic iPSC clones, using a Sendai virus-based vector, starting from fibroblasts of a patient carrying a dominant mutation in IFIH1. All lines were characterized for genomic integrity, genetic uniqueness, pluripotency, and differentiation capability. Our clones might offer a good model to investigate AGS7 pathophysiological mechanism and to discover new biomarkers for this condition treatment.

Amphiphysin-IgG autoimmune neuropathy: A recognizable clinicopathologic syndrome.

OBJECTIVE: To define the clinicopathologic features of amphiphysin-immunoglobulin G (IgG)-mediated neuropathy. METHODS: Patients examined at our institution from January 1, 1995, to September 30, 2018, with amphiphysin-IgG by indirect immunofluorescence and Western blot, were reviewed. Their phenotypes were compared to cases of coexisting collapsin response-mediator protein-5 (CRMP5)-IgG or anti-neuronal nuclear antibody type 1 (ANNA1-IgG) and CRMP5-IgG autoimmunity. Improvement in modified Rankin Scale (mRS) (≥1) on follow-up was considered a favorable outcome. Amphiphysin RNA expression was assessed in healthy nerves. RESULTS: Fifty-three amphiphysin-IgG-positive cases were identified. Of 33 (60%) patients with neuropathy, 21 had amphiphysin-IgG alone, and 12 had coexisting autoantibodies (ANNA1-IgG, n = 8; CRMP5-IgG, n = 2; ANNA1-IgG and CRMP5-IgG, n = 2). The neuropathies in isolated amphiphysin-IgG autoimmunity included polyradiculoneuropathy (62%), diffuse sensory neuronopathy (35%), and facial neuropathy with gastroparesis (3%). Among these, pain (80%), breast cancer (63%), and CNS (57%) involvements commonly coexisted, and neuropathy frequently prompted breast cancer diagnosis (76%). Stiff-person spectrum disorder was the most common CNS accompaniment (45%). Nerve biopsies showed axonal loss (n = 6/6), subperineurial edema (n = 4/6), and CD4 predominant inflammation (n = 2/6). Median mRS score at last follow-up was 3.5; 58% of patients were immunotherapy-responsive. Patients with amphiphysin-IgG alone had more favorable immunotherapy response than patients with CRMP5-IgG polyneuropathy (n = 45) (44% vs 16%, p = 0.028, odds ratio 4.2, 95% confidence interval 1.1 to 15.5). Only 1/9 (11%) patients with amphiphysin-IgG with coexisting CRMP5-IgG or ANNA1-IgG had immunotherapy response. RNA amphiphysin expression occurred at low levels in nerve. CONCLUSION: Amphiphysin-IgG autoimmune neuropathy has a recognizable phenotype, is frequently immune responsive, and can prompt early diagnosis of breast cancer.

Neurochondrin neurological autoimmunity.

OBJECTIVES: To describe the neurologic spectrum and treatment outcomes for neurochondrin-IgG positive cases identified serologically in the Mayo Clinic Neuroimmunology Laboratory. METHODS: Archived serum and CSF specimens previously scored positive for IgGs that stained mouse hippocampal tissue in a nonuniform synaptic pattern by immunofluorescence assay (89 among 616,025 screened, 1993-2019) were reevaluated. Antibody characterization experiments revealed specificity for neurochondrin, confirmed by recombinant protein assays. RESULTS: IgG in serum (9) or CSF (4) from 8 patients yielded identical neuron-restricted CNS patterns, most pronounced in hippocampus (stratum lucidum in particular), cerebellum (Purkinje cells and molecular layer), and amygdala. All were neurochondrin-IgG positive. Five were women; median symptom onset age was 43 years (range, 30-69). Of 7 with clinical data, 6 presented with rapidly progressive cerebellar ataxia, brainstem signs, or both; 1 had isolated unexplained psychosis 1 year prior. Five of 6 had cerebellar signs, 4 with additional brainstem symptoms or signs (eye movement abnormalities, 3; dysphagia, 2; nausea and vomiting, 1). One patient with brainstem signs (vocal cord paralysis and VII nerve palsy) had accompanying myelopathy (longitudinally extensive abnormality on MRI; aquaporin-4-IgG and myelin oligodendrocyte glycoprotein-IgG negative). The 7th patient had small fiber neuropathy only. Just 1 of 7 had contemporaneous cancer (uterine). Six patients with ataxia or brainstem signs received immunotherapy, but just 1 remained ambulatory. At last follow-up, 5 had MRI evidence of severe cerebellar atrophy. CONCLUSION: In our series, neurochondrin autoimmunity was usually accompanied by a nonparaneoplastic rapidly progressive rhombencephalitis with poor neurologic outcomes. Other phenotypes and occasional paraneoplastic causes may occur.

Updating Neuroimmune Targets in Central Nervous System Dysfunction.

Disorders of the central nervous system (CNS) have many etiologies compounded by limited options for treatment. The lack of successful treatments for these disorders stems from the difficulty of gaining effective access to the CNS through the blood-brain barrier, and the irreplaceable nature of neurons. Here, we review recent advances in the field of neuroimmunology and discuss novel strategies for targeting microglia, meningeal lymphatics, and the peripheral immune system that may lead to successful treatment of a broad range of CNS disorders. In the future, it will be important to continue to explore the vast communications between the CNS and the immune system to map out dysfunctions that attribute to diseases such as chronic neuroinflammation, autoimmunity, CNS injury, and more.