Hypothalamic-Bulbar MRI Hyperintensity in Anti-IgLON5 Disease with Serum-Restricted Antibodies: A Case Report and Systematic Review of Literature

Case report: anti-IgLON5 disease combined with paraneoplastic cerebellar degeneration with the detection of anti-sulfatide IgG antibody, masquerading as meningoencephalitis

OBJECTIVE

Anti-IgLON5 disease is a rare autoimmune mediated disease. It is mainly featured by sleep-related disturbance, parkinsonism, chorea and limb ataxia. Previous studies had clarified its clinical manifestations and predisposing genes. However, as far as we know, anti-IgLON5 disease combined with paraneoplastic cerebellar degeneration (PCD) with the detection of anti-Sulfatide IgG antibody, masquerading as meningoencephalitis had not been reported before.

CASE PRESENTATION

A 57-year-old Chinese female presented with walking unsteadily for 12 days and logagnosia for 2 days and was admitted to our hospital. She had a past history of breast cancer. Magnetic resonance imaging (MRI) revealed leptomeningeal enhancement (prominent in cerebellar hemisphere). Arterial spin labeling (ASL) perfusion showed hyperperfusion in the cerebellar hemisphere and interhemispheric fissure cistern. MRI and ASL indicated the diagnosis was meningoencephalitis. However, IgG anti-IgLON5 antibody was positive in both serum and cerebrospinal fluid. Therefore, the diagnosis was anti-IgLON5 disease. In addition, the patient combined with PCD due to positive anti-Yo-antibody in serum fluid .

CONCLUSIONS

Whereas sleep disturbance is the most common feature in patients with anti-IgLON5 disease, our case presented with walking unsteadily and logagnosia. Anti-IgLON5 disease combined with PCD with the detection of anti-Sulfatide IgG antibody, masquerading as meningoencephalitis is very rare. Therefore, if meningoencephalitis did not recover with conventional treatment, anti-IgLON5 disease and PCD should be considered as the differential diagnosis.

A rare pediatric patient of anti-IgLON5 encephalitis with epileptic seizures as the first symptom

BACKGROUND

Anti-IgLON5 encephalitis was a rare neurological and heterogeneous disorder, which was mainly found in adults. Epileptic seizures related to anti-IgLON5 disease were rarely reported.

METHODS

Neural antibodies associated with autoimmune encephalitis in serum and cerebrospinal fluid (CSF) were tested using cell-based assays (CBA) with immunofluorescence double staining. The antibodies in serum were further confirmed by tissue-based assay (TBA) with rat brain and kidney tissue.

RESULTS

We reported a pediatric case presented with epileptic seizures, cognitive impairments, and sleep disorders. Autoantibody screening showed anti-IgLON5 antibody IgG (1:100+) and anti-NMDAR antibody IgG (1:10+) in the serum. She was diagnosed as anti-IgLON5 encephalitis. Her conditions improved rapidly by treated with intravenous immunoglobulin and high dose intravenous methylprednisolone.

CONCLUSION

We described the second pediatric case with anti-IgLON5 encephalitis, who was also the first presented with epileptic seizures as the initial presentation. Anti-IgLON5 encephalitis might have mild manifestations. For patients with new onset seizures associated with cognitive impairments and sleep disturbances, anti-IgLON5 antibody should be tested as early, even in children.

Anti-IgLON5 disease with severe central sleep apnea-hypopnea syndrome: A case report

Anti-IgLON family protein 5 (IgLON5) antibody-related encephalitis is a rare but increasingly recognized central nervous system autoimmune disease. It displays heterogeneity in clinical presentation. As the clinical case repository expands, our understanding of the disease's clinical phenotypes and therapeutic approaches continues to evolve. This report details a 73-year-old male's case, initially misdiagnosed with narcolepsy due to excessive daytime sleepiness and sleep-related involuntary behaviors, but later found to have severe respiratory disturbances, diverging from narcolepsy. During treatment, the patient's condition progressed to respiratory failure, necessitating further investigation. Diagnosis was confirmed through positive serum and cerebrospinal fluid (CSF) tests for anti-IgLON5 antibodies. Treatment with continuous positive airway pressure (CPAP), immunoglobulin pH4, and corticosteroids significantly improved his condition. This case underscores the critical need for awareness of anti-IgLON5 encephalitis within the differential diagnosis of complex sleep disorders, highlighting its potential for severe progression and the challenges associated with its diagnosis.

Upper airway manifestations of anti-IgLON5 disease: Otorhinolaryngological point of view

INTRODUCTION

Anti-IgLON5 disease is a recently described neurological disorder with multisystemic features. The disease is characterized by the presence of IgLON5 antibodies in serum and cerebrospinal fluid. Our objective is to describe in detail the otorhinolaryngological manifestations of this disease, which are frequent and may include dysphagia, dysarthria, vocal cord paralysis and laryngospasm.

METHODS

In this study, we present a series of 9 patients with anti-IgLON5 disease and otolaryngological manifestations. Patients were evaluated between July 2012 and March 2022 by video-polysomnography, fiber-optic laryngoscopy, and functional endoscopic evaluation of swallowing.

RESULTS

The median age was 71 years, and 5 (56%) were female. Video-polysomnography showed a NREM/REM parasomnia in 6 patients (67%), obstructive sleep apnea in 8 (88%), stridor during sleep in 7 (78%) and central apneas in 1 (11%). Six out of the 9 patients (67%) presented episodes of acute respiratory failure that required mechanical ventilation, 6 had vocal fold palsy with 4 of them requiring tracheostomy (3 had to be performed on an emergency basis). Dysphagia occurred in 8 patients (89%). Prominent upper airway secretion and sialorrhea was also present in 3 cases.

CONCLUSION

The anti-IgLON5 disease exhibits extensive otolaryngological symptoms, mainly affecting the upper airway. These symptoms affect the quality of life and can be life-threatening. Prompt acute management is essential for stridor, dyspnea, and dysphagia. Given the potential severity of the symptoms and rarity of the disease, it is important for otolaryngologists to be familiar with anti-IgLON5 disease.

LEVEL OF EVIDENCE

Level 4.

HLA-DQB1*05 subtypes and not DRB1*10:01 mediates risk in anti-IgLON5 disease

Anti-IgLON5 disease is a rare and likely underdiagnosed subtype of autoimmune encephalitis. The disease displays a heterogeneous phenotype that includes sleep, movement and bulbar-associated dysfunction. The presence of IgLON5-antibodies in CSF/serum, together with a strong association with HLA-DRB1*10:01∼DQB1*05:01, supports an autoimmune basis. In this study, a multicentric human leukocyte antigen (HLA) study of 87 anti-IgLON5 patients revealed a stronger association with HLA-DQ than HLA-DR. Specifically, we identified a predisposing rank-wise association with HLA-DQA1*01:05∼DQB1*05:01, HLA-DQA1*01:01∼DQB1*05:01 and HLA-DQA1*01:04∼DQB1*05:03 in 85% of patients. HLA sequences and binding cores for these three DQ heterodimers were similar, unlike those of linked DRB1 alleles, supporting a causal link to HLA-DQ. This association was further reflected in an increasingly later age of onset across each genotype group, with a delay of up to 11 years, while HLA-DQ-dosage dependent effects were also suggested by reduced risk in the presence of non-predisposing DQ1 alleles. The functional relevance of the observed HLA-DQ molecules was studied with competition binding assays. These proof-of-concept experiments revealed preferential binding of IgLON5 in a post-translationally modified, but not native, state to all three risk-associated HLA-DQ receptors. Further, a deamidated peptide from the Ig2-domain of IgLON5 activated T cells in two patients, compared with one control carrying HLA-DQA1*01:05∼DQB1*05:01. Taken together, these data support a HLA-DQ-mediated T-cell response to IgLON5 as a potentially key step in the initiation of autoimmunity in this disease.

HLA dependency and possible clinical relevance of intrathecally synthesized anti-IgLON5 IgG4 in anti-IgLON5 disease

Background

Anti-IgLON5 disease is a rare chronic autoimmune disorder characterized by IgLON5 autoantibodies predominantly of the IgG4 subclass. Distinct pathogenic effects were described for anti-IgLON5 IgG1 and IgG4, however, with uncertain clinical relevance.

Methods

IgLON5-specific IgG1-4 levels were measured in 46 sera and 20 cerebrospinal fluid (CSF) samples from 13 HLA-subtyped anti-IgLON5 disease patients (six females, seven males) using flow cytometry. Intervals between two consecutive serum or CSF samplings (31 and 10 intervals, respectively) were categorized with regard to the immunomodulatory treatment active at the end of the interval, changes of anti-IgLON5 IgG1 and IgG4 levels, and disease severity. Intrathecal anti-IgLON5 IgG4 synthesis (IS) was assessed using a quantitative method.

Results

The median age at onset was 66 years (range: 54-75), disease duration 10 years (range: 15-156 months), and follow-up 25 months (range: 0-83). IgLON5-specific IgG4 predominance was observed in 38 of 46 (83%) serum and 11 of 20 (55%) CSF samples. Anti-IgLON5 IgG4 levels prior clinical improvement in CSF but not serum were significantly lower than in those prior stable/progressive disease. Compared to IgLON5 IgG4 levels in serum, CSF levels in HLA-DRB1*10:01 carriers were significantly higher than in non-carriers. Indeed, IgLON5-specific IgG4 IS was demonstrated not only in four of five HLA-DRB1*10:01 carriers but also in one non-carrier. Immunotherapy was associated with decreased anti-IgGLON5 IgG serum levels. In CSF, lower anti-IgLON5 IgG was associated with immunosuppressive treatments used in combination, that is, corticosteroids and/or azathioprine plus intravenous immunoglobulins or rituximab.

Conclusion

Our findings might indicate that CSF IgLON5-specific IgG4 is frequently produced intrathecally, especially in HLA-DRB1*10:01 carriers. Intrathecally produced IgG4 may be clinically relevant. While many immunotherapies reduce serum IgLON5 IgG levels, more intense immunotherapies induce clinical improvement and may be able to target intrathecally produced anti-IgLON5 IgG. Further studies need to confirm whether anti-IgLON5 IgG4 IS is a suitable prognostic and predictive biomarker in anti-IgLON5 disease.

The psychiatric symptoms in anti-IgLON5 disease: Case report and literature review

Immunotherapy may be ineffective in the advanced stages of anti-IgLON5 disease with psychiatric symptoms. The psychiatric symptoms in advanced stages of anti-IgLON5 disease may be associated with neurodegeneration.

Anti-IgLON5 disease: a novel topic beyond neuroimmunology

Anti-IgLON5 disease is a recently defined autoimmune disorder of the nervous system associated with autoantibodies against IgLON5. Given its broad clinical spectrum and extremely complex pathogenesis, as well as difficulties in its early diagnosis and treatment, anti-IgLON5 disease has become the subject of considerable research attention in the field of neuroimmunology. Anti-IgLON5 disease has characteristics of both autoimmunity and neurodegeneration due to the unique activity of the anti-IgLON5 antibody. Neuropathologic examination revealed the presence of a tauopathy preferentially affecting the hypothalamus and brainstem tegmentum, potentially broadening our understanding of tauopathies. In contrast to that seen with other autoimmune encephalitis-related antibodies, basic studies have demonstrated that IgLON5 antibody-induced neuronal damage and degeneration are irreversible, indicative of a potential link between autoimmunity and neurodegeneration in anti-IgLON5 disease. Herein, we comprehensively review and discuss basic and clinical studies relating to anti-IgLON5 disease to better understand this complicated disorder.

Disorders of arousal and sleep-related hypermotor epilepsy - overview and challenges night is a battlefield of sleep and arousal promoting forces

Arousability and reactivity to sensory stimuli are essential features of sleep, discriminating it from coma and keeping the sleeper in contact with the environment. Arousals and oscillations during sleep serve the reversibility of sleep and carry an alarm function awakening the sleeper in danger. In this review, we will explore mechanisms and circuits involved in arousal intrusions within the sleep texture, focusing on the significance of these phenomena in two sleep-related conditions: NREM sleep parasomnias and sleep-related hypermotor epilepsy. Knowledges and gaps in the field are discussed.

Case Report: Neuropsychological Findings in IgLON5 Antibody Disorder

IgLON5 antibody encephalopathy is a rare but increasingly recognized disorder with a variety of clinical signs. Typical symptoms are sleep disorder, gait disturbances, signs of bulbar dysfunction and a variety of neurological symptoms like oculomotor abnormalities and movement disorders. In addition, cognitive decline can be a prominent symptom. So far, there are only a few studies that have dealt with the course and possible treatment options of IgLON5 antibody encephalopathy. In this study the clinical case of a female patient with IgLON5 antibody disease and the response to treatment is described. Here we report on the case of a 67-year-old female patient who showed cognitive deterioration, gait difficulties, and chronic obstructive sleep disorder. The diagnostic course showed a positive anti-IgLON5 serum and anti-IgLON5 IgG antibodies in cerebrospinal fluid. The patient was subsequently treated with high dosage i.v. methylprednisolone, i.v. immunoglobulins and plasmapheresis. Neuropsychological tests showed cognitive deficits in different domains, including verbal and visual memory. Both, neuropsychological deficits and antibody titer, showed an improvement after plasmapheresis. The presented case shows that IgLON5 disease can present with rapidly progressing cognitive deterioration as the prominent symptom, adding to the variety of clinical signs in this disorder. Testing for IgLON5-antibodies should be considered in patients with progressing cognitive decline, especially if accompanied by sleep disorders or neurological symptoms like oculomotor abnormalities, dysautonomia or bulbar signs.