JAK Inhibitors in Rheumatology: Implications for Paediatric Syndromes?

Treatment of non-systemic juvenile idiopathic arthritis

In the past two decades, the treatment of juvenile idiopathic arthritis (JIA) has evolved markedly, owing to the availability of a growing number of novel, potent and relatively safe therapeutic agents and the shift of management strategies towards early achievement of disease remission. However, JIA encompasses a heterogeneous group of diseases that require distinct treatment approaches. Furthermore, some old drugs, such as methotrexate, sulfasalazine and intraarticular glucocorticoids, still maintain an important therapeutic role. In the past 5 years, information on the efficacy and safety of drug therapies for JIA has been further enriched through the accomplishment of several randomized controlled trials of newer biologic and synthetic targeted DMARDs. In addition, a more rational therapeutic approach has been fostered by the promulgation of therapeutic recommendations and guidelines. A multinational collaborative effort has led to the development of the recommendations for the treat-to-target strategy in JIA. There is currently increasing interest in establishing the optimal time and modality for discontinuation of treatment in children with JIA who achieve sustained clinical remission. The aim of this Review is to summarize the current evidence and discuss the therapeutic approaches to the management of non-systemic phenotypes of JIA, including oligoarthritis, polyarthritis, enthesitis-related arthritis and psoriatic arthritis.

Interferon-α receptor antisense oligonucleotides reduce neuroinflammation and neuropathology in a mouse model of cerebral interferonopathy

Chronic and elevated levels of the antiviral cytokine IFN-α in the brain are neurotoxic. This is best observed in patients with genetic cerebral interferonopathies such as Aicardi-Goutières syndrome. Cerebral interferonopathies typically manifest in early childhood and lead to debilitating disease and premature death. There is no cure for these diseases with existing treatments largely aimed at managing symptoms. Thus, an effective therapeutic strategy is urgently needed. Here, we investigated the effect of antisense oligonucleotides targeting the murine IFN-α receptor (Ifnar1 ASOs) in a transgenic mouse model of cerebral interferonopathy. Intracerebroventricular injection of Ifnar1 ASOs into transgenic mice with brain-targeted chronic IFN-α production resulted in a blunted cerebral interferon signature, reduced neuroinflammation, restoration of blood-brain barrier integrity, absence of tissue destruction, and lessened neuronal damage. Remarkably, Ifnar1 ASO treatment was also effective when given after the onset of neuropathological changes, as it reversed such disease-related features. We conclude that ASOs targeting the IFN-α receptor halt and reverse progression of IFN-α-mediated neuroinflammation and neurotoxicity, opening what we believe to be a new and promising approach for the treatment of patients with cerebral interferonopathies.

Janus Kinase Inhibitors and Interstitial Lung Disease Associated With Pediatric Rheumatic Diseases: An Unexplored Field

Rheumatic diseases are often complicated by lung disease, commonly presenting as interstitial lung disease (ILD), with potentially detrimental consequences for patient survival. Although less frequent in pediatric patients, pulmonary involvement may be observed in almost all childhood-onset rheumatic conditions. The development of biological disease-modifying anti-rheumatic drugs has significantly improved clinical outcomes. However, disease remission is not always complete or long-lasting, and treatment may need to be discontinued due to adverse effects. A novel class of drugs, namely Janus kinase inhibitors (JAKis), has been proposed to provide a significant survival benefit for patients with rheumatic diseases. Despite the ample literature on the efficacy and safety of JAKis in rheumatic disease, only a few studies have investigated the effectiveness of these drugs in patients with pulmonary involvement, and only two case reports have presented results in pediatric patients. We provide an overview of the rationale for using JAKis in ILDs associated with rheumatic disease and summarize the main studies evaluating their efficacy in both adult and pediatric patients. The present review highlights the need for controlled long-term studies to assess the efficacy and safety of JAKis in pediatric rheumatic disease complicated by lung disease.

JAK Inhibition in Juvenile Idiopathic Arthritis (JIA): Better Understanding of a Promising Therapy for Refractory Cases

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases with probably differential underlying physiopathology. Despite the revolutionary era of biologics, some patients remain difficult to treat because of disease severity, drug adverse events, drug allergy or association with severe comorbidities, i.e., uveitis, interstitial lung disease and macrophagic activation syndrome. Janus Kinase (JAK) inhibitors are small molecules that target JAK/Signal Transducers and Activators of Transcription (STAT) pathways, which could then prevent the activity of several proinflammatory cytokines. They may provide a useful alternative in these cases of JIA or in patients actually affected by Mendelian disorders mimicking JIA, such as type I interferonopathies with joint involvement, and might be the bridge for haematopoietic stem cell transplantation in these disabling conditions. As these treatments may have side effects that should not be ignored, ongoing and further controlled studies are still needed to provide data underlying long-term safety considerations in children and delineate subsets of JIA patients that will benefit from these promising treatments.

Breaking down the cellular responses to type I interferon neurotoxicity in the brain

Since their original discovery, type I interferons (IFN-Is) have been closely associated with antiviral immune responses. However, their biological functions go far beyond this role, with balanced IFN-I activity being critical to maintain cellular and tissue homeostasis. Recent findings have uncovered a darker side of IFN-Is whereby chronically elevated levels induce devastating neuroinflammatory and neurodegenerative pathologies. The underlying causes of these 'interferonopathies' are diverse and include monogenetic syndromes, autoimmune disorders, as well as chronic infections. The prominent involvement of the CNS in these disorders indicates a particular susceptibility of brain cells to IFN-I toxicity. Here we will discuss the current knowledge of how IFN-Is mediate neurotoxicity in the brain by analyzing the cell-type specific responses to IFN-Is in the CNS, and secondly, by exploring the spectrum of neurological disorders arising from increased IFN-Is. Understanding the nature of IFN-I neurotoxicity is a crucial and fundamental step towards development of new therapeutic strategies for interferonopathies.

Assessment of type I interferon signatures in undifferentiated inflammatory diseases: A Japanese multicenter experience

Purpose

Upregulation of type I interferon (IFN) signaling has been increasingly detected in inflammatory diseases. Recently, upregulation of the IFN signature has been suggested as a potential biomarker of IFN-driven inflammatory diseases. Yet, it remains unclear to what extent type I IFN is involved in the pathogenesis of undifferentiated inflammatory diseases. This study aimed to quantify the type I IFN signature in clinically undiagnosed patients and assess clinical characteristics in those with a high IFN signature.

Methods

The type I IFN signature was measured in patients’ whole blood cells. Clinical and biological data were collected retrospectively, and an intensive genetic analysis was performed in undiagnosed patients with a high IFN signature.

Results

A total of 117 samples from 94 patients with inflammatory diseases, including 37 undiagnosed cases, were analyzed. Increased IFN signaling was observed in 19 undiagnosed patients, with 10 exhibiting clinical features commonly found in type I interferonopathies. Skin manifestations, observed in eight patients, were macroscopically and histologically similar to those found in proteasome-associated autoinflammatory syndrome. Genetic analysis identified novel mutations in the PSMB8 gene of one patient, and rare variants of unknown significance in genes linked to type I IFN signaling in four patients. A JAK inhibitor effectively treated the patient with the PSMB8 mutations. Patients with clinically quiescent idiopathic pulmonary hemosiderosis and A20 haploinsufficiency showed enhanced IFN signaling.

Conclusions

Half of the patients examined in this study, with undifferentiated inflammatory diseases, clinically quiescent A20 haploinsufficiency, or idiopathic pulmonary hemosiderosis, had an elevated type I IFN signature.

Implications of SARS-CoV-2 Infection in Systemic Juvenile Idiopathic Arthritis

Systemic juvenile idiopathic arthritis (sJIA) is a serious multifactorial autoinflammatory disease with a significant mortality rate due to macrophage activation syndrome (MAS). Recent research has deepened the knowledge about the pathophysiological mechanisms of sJIA-MAS, facilitating new targeted treatments, and biological disease-modifying antirheumatic drugs (bDMARDs), which significantly changed the course of the disease and prognosis. This review highlights that children are less likely to suffer severe COVID-19 infection, but at approximately 2–4 weeks, some cases of multisystem inflammatory syndrome in children (MIS-C) have been reported, with a fulminant course. Previous established treatments for cytokine storm syndrome (CSS) have guided COVID-19 therapeutics. sJIA-MAS is different from severe cases of COVID-19, a unique immune process in which a huge release of cytokines will especially flood the lungs. In this context, MIS-C should be reinterpreted as a special MAS, and long-term protection against SARS-CoV-2 infection can only be provided by the vaccine, but we do not yet have sufficient data. COVID-19 does not appear to have a substantial impact on rheumatic and musculoskeletal diseases (RMDs) activity in children treated with bDMARDs, but the clinical features, severity and outcome in these patients under various drugs are not yet easy to predict. Multicenter randomized controlled trials are still needed to determine when and by what means immunoregulatory products should be administered to patients with sJIA-MAS with a negative corticosteroid response or contraindications, to optimize their health and safety in the COVID era.

Evaluating the use of JAK inhibitors in inflammatory connective tissue diseases in pediatric patients: an update

INTRODUCTION

Connective tissue diseases (CTDs) are a category of conditions that affect tissues that support and provide structure to the body. These diseases include rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, and sclerosing diseases. CTDs can be caused by dysregulation of inflammatory pathways, specifically an upregulation of interferons and JAK/STAT pathway activation.

AREAS COVERED

While CTDs have historically been treated with broadly immunosuppressant medications such as corticosteroids and disease-modifying antirheumatic drugs (DMARDS), newer and more targeted immunomodulating medications called Janus kinase inhibitors (JAKi), have emerged as potential treatments.

EXPERT OPINION

While most studies regarding JAKi for CTDs have focused on adult populations, pediatric patients with CTDs may also benefit from JAKi therapy. Moreover, the JAK/STAT inhibitor tofacitinib has been approved by the FDA for the treatment of active polyarticular course juvenile idiopathic arthritis. In this review, we have summarized what has been published on the use of JAKi for various pediatric CTDs.

Transition readiness assessment in adolescents and young adults with rheumatic diseases: The Singapore experience

BACKGROUND

Transition from pediatric to adult care is a challenging time for adolescents and young adults (AYA) with rheumatic diseases. Validated tools have been developed to assess transition readiness.

AIM

To evaluate transition readiness among AYA with rheumatic diseases and to identify factors associated with transition readiness.

METHODS

Patients ≥15 years old were enrolled into our transition program and administered a Transition Readiness Assessment Tool (TRAT) from July 2017. The TRAT consists of 3 components: (a) patient's perception on importance of transition and confidence toward transition on a Likert scale 0-10; (b) assessment of knowledge on medical and healthcare usage using a set of 23 questions; (c) transition readiness using the Transition Readiness Assessment Questionnaire (TRAQ). Differences between groups were compared to identify factors associated with transition readiness.

RESULTS

Transition readiness assessment was performed in 152 patients. The median score for perception on transition importance was 7.0 (5.0-8.8) and the median score for confidence in transition was 7.0 (5.0-9.0). Majority of the patients (>50%) lack knowledge in health insurance, carrying health information, healthcare privacy changes and making own healthcare decision. Patients <20 years old were also deficient in knowledge in navigating healthcare systems. TRAQ scores were lowest in areas pertaining to healthcare insurance and obtaining financial help.

CONCLUSION

Healthcare insurance literacy and self-management skills were lacking in the assessment of transition readiness in AYA with rheumatic diseases. Targeted intervention in these areas will improve transition readiness and promote successful transition processes.

Pathogenesis and Treatment of Refractory Disease Courses in Systemic Juvenile Idiopathic Arthritis: Refractory Arthritis, Recurrent Macrophage Activation Syndrome and Chronic Lung Disease

Systemic juvenile idiopathic arthritis is a distinct and heterogeneous disease presently classified under the umbrella of juvenile idiopathic arthritis, with some patients following a monophasic remitting course, whereas others have persistent disease with chronic organ- and life-threatening complications. Although biologic therapies have revolutionized treatment, recent follow-up studies report significant numbers of children with persistently active disease on long term follow-up. This review focuses on refractory disease courses, specifically refractory arthritis, systemic juvenile idiopathic arthritis with recurrent, or longstanding signs of macrophage activation syndrome, and systemic juvenile idiopathic arthritis associated with suspected, probable, or definite lung disease.

Interfering with interferons: targeting the JAK-STAT pathway in complications of systemic juvenile idiopathic arthritis (SJIA)

Systemic JIA (SJIA) is distinguished from other forms of JIA by the prevalence of the severe, life-threatening complications macrophage activation syndrome (SJIA-MAS) and lung disease (SJIA-LD). Alternative therapeutics are urgently needed, as disease pathogenesis diverges from what is observed in SJIA, and currently available biologics are insufficient. SJIA-MAS, defined by a cytokine storm and dysregulated proliferation of T-lymphocytes, and SJIA-LD which presents with lymphocytic interstitial inflammation and pulmonary alveolar proteinosis, are both thought to be driven by IFNs, in particular the type II IFN-γ. Involvement of IFNs and a possible crosstalk of type I IFNs with existing biologics indicate a distinct role for the JAK-STAT signalling pathway in the pathogenesis of SJIA-MAS and SJIA-LD. Here, we review this role of JAK-STATs and IFNs in SJIA complications and discuss how new insights of ongoing research are shaping future therapeutic advances in the form of JAK inhibitors and antibodies targeting IFNs.

Advancing the treatment of juvenile idiopathic arthritis

Treatment for juvenile idiopathic arthritis has undergone substantial changes in recent decades. These changes are partly due to the availability of new treatments, mainly biological agents, as well as developments in treatment strategies, including a focus on concepts such as treat-to-target. In addition, the creation of large paediatric research networks has improved patient access to, and design of, clinical trials for rare paediatric diseases. Although these advances have resulted in improvements in care for most patients with juvenile idiopathic arthritis, certain subgroups of patients continue to have a poor prognosis. Further research aims to identify patients in these subgroups early, to personalise their care, improve functional outcomes, and minimise long-term damage and harm. Optimising the duration of therapy for those individuals who require systemic immunosuppression is also of importance. Incorporation of novel biomarkers in combination with validated clinical measures in an effort to predict outcomes and target therapy accordingly is an exciting development.

The Coming-of-Age Transition Care for Adolescents with Rheumatic Disease-Where Are We and What Have We Done in Asia?

The transition from pediatric to adult health care is a challenging yet important process in rheumatology as most childhood-onset rheumatic diseases persist into adulthood. Numerous reports on unmet needs as well as evidence of negative impact from poor transition have led to increased efforts to improve transition care, including international guidelines and recommendations. In line with these recommendations, transition programs along with transition readiness assessment tools have been established. Despite these efforts, there are still a lot of work to be done for transition care in rheumatology. This review article focuses on how transition care in rheumatology has developed in recent years and highlights the gaps in current practices.

Beyond the guidelines management of juvenile idiopathic arthritis: a case report of a girl with polyarticular disease refractory to multiple treatment options and Leri Weill syndrome

BACKGROUND

The last two decades brought new treatment options and high quality guidelines into the paediatric rheumatologic practice. Nevertheless, a number of patients still present a diagnostic and therapeutic challenge due to combination of vague symptoms and unresponsiveness to available treatment modalities.

CASE PRESENTATION

We report a case of sixteen years old girl suffering from polyarticular type of juvenile idiopathic arthritis refractory to multiple treatment options. She first presented at the age of 4 with swelling and contractures of both knees. Her symptoms were initially unresponsive to nonsteroidal anti-inflammatory drugs and progressed despite treatment with intraarticular and systemic glucocorticoids and methotrexate. Throughout the years, she received several biologics together with continuous administration of nonsteroidal anti-inflammatory drugs and disease modifying anti-rheumatic drugs as well as intraarticular and systemic glucocorticoids in disease flares. However, none of this options  provided a permanent remission, so various other modalities, as well as other possible diagnoses were constantly being considered. Eventually she became dependent on a daily dose of systemic glucocorticoids. In 2018, the treatment with Janus kinase inhibitor tofacitinib was initiated, which led to gradual amelioration of musculoskeletal symptoms, improvement of inflammatory markers and overall well-being, as well as to the weaning of systemic glucocorticoids. As the swelling of the wrists subsided for the first time in many years, Madelung's deformity was noticed, first clinically, and later radiographically as well. Genetic analysis revealed short-stature homeobox gene deficiency and confirmed the diagnosis of Leri Weill syndrome.

CONCLUSIONS

This case report emphasizes the need for reporting refractory, complicated cases from everyday clinical practice in order to build-up the overall knowledge and share experience which is complementary to available guidelines. Individual reports of difficult to treat cases, especially when additional diagnoses are involved, can be helpful for physicians treating patients with common rheumatological diseases such as juvenile idiopathic arthritis.

Case Report: The JAK-Inhibitor Ruxolitinib Use in Aicardi-Goutieres Syndrome Due to ADAR1 Mutation

Type I Interferonopathies comprise inherited inflammatory diseases associated with perturbation of the type I IFN response. Use of Janus kinase (JAK) inhibitors has been recently reported as possible tools for treating some of those rare diseases. We describe herein the clinical picture and treatment response to the JAK-inhibitor ruxolitinib in a 5-year-old girl affected by Aicardi-Goutières Syndrome type 6 (AGS6) due to ADAR1 mutation. The girl's interferon score (IS) was compared with that of her older brother, suffering from the same disorder, who was not treated. We observed a limited, but distinct neurological improvement (Gross Motor Function and Griffiths Mental Development Scales). Analysis of IS values of the two siblings during the treatment showed several changes, especially related to infections; the IS values of the child treated with ruxolitinib were consistently lower than those measured in her brother. Based on these observations we suggest that the use of ruxolitinib in children with the same condition might be effective in inhibiting type I interferon response and that starting this therapy at early age in children with AGS could mitigate the detrimental effects of type I interferon hyperproduction.

Multidisciplinary Guidance Regarding the Use of Immunomodulatory Therapies for Acute Coronavirus Disease 2019 in Pediatric Patients

BACKGROUND

Immune-mediated lung injury and systemic hyperinflammation are characteristic of severe and critical coronavirus disease 2019 (COVID-19) in adults. Although the majority of severe acute respiratory syndrome coronavirus 2 infections in pediatric populations result in minimal or mild COVID-19 in the acute phase of infection, a small subset of children develop severe and even critical disease in this phase with concomitant inflammation that may benefit from immunomodulation. Therefore, guidance is needed regarding immunomodulatory therapies in the setting of acute pediatric COVID-19. This document does not provide guidance regarding the recently emergent multisystem inflammatory syndrome in children (MIS-C).

METHODS

A multidisciplinary panel of pediatric subspecialty physicians and pharmacists with expertise in infectious diseases, rheumatology, hematology/oncology, and critical care medicine was convened. Guidance statements were developed based on best available evidence and expert opinion.

RESULTS

The panel devised a framework for considering the use of immunomodulatory therapy based on an assessment of clinical disease severity and degree of multiorgan involvement combined with evidence of hyperinflammation. Additionally, the known rationale for consideration of each immunomodulatory approach and the associated risks and benefits was summarized.

CONCLUSIONS

Immunomodulatory therapy is not recommended for the majority of pediatric patients, who typically develop mild or moderate COVID-19. For children with severe or critical illness, the use of immunomodulatory agents may be beneficial. The risks and benefits of such therapies are variable and should be evaluated on a case-by-case basis with input from appropriate specialty services. When available, the panel strongly favors immunomodulatory agent use within the context of clinical trials. The framework presented herein offers an approach to decision-making regarding immunomodulatory therapy for severe or critical pediatric COVID-19 and is informed by currently available data, while awaiting results of placebo-controlled randomized clinical trials.

Treatment of Juvenile Spondyloarthritis: Where We Stand

Juvenile spondyloarthritis is a subset of juvenile idiopathic arthritis (JIA) with onset in late childhood and adolescence and a strong association with human leukocyte antigen (HLA) B-27 positivity and familial aggregation that has the potential for axial involvement, potentially leading to ankylosing spondylitis. Current therapy for severe disease relies heavily on tumor necrosis factor inhibitors (TNFi). Treatment paradigms in children largely consist of extrapolation from studies on adults with spondyloarthritis. Additional therapies studied in adults include non-steroidal anti-inflammatory drugs (NSAIDs), blockade of the interleukin-17 (IL-17) and IL-23 axes, blockade of T-cell stimulation, phosphodiesterase (PDE)-4 inhibition, and Janus-activated kinase (JAK) pathway alteration. IL-17 blockade and IL-23 blockade are guideline approved after TNFi failure (and even as an alternative to TNFi) in adults, depending on concomitant inflammatory bowel and skin disease, with JAK and PDE-4 inhibition options following biologic failure. Neither pediatric nor adult guidelines address IL-6 blockade, T-cell co-stimulation blockade, or combination biologic therapy.

Current and emerging biologics for the treatment of juvenile idiopathic arthritis

INTRODUCTION

The management of a child with juvenile idiopathic arthritis (JIA) requires a combination of pharmacological, physical, and psychosocial therapies in order to induce disease remission, by controlling articular and systemic inflammation. This review aims to provide a comprehensive discussion on the biological therapies currently in use in the treatment of JIA referring to existing recommendations and clinical evidence. We also discuss on the emerging biological drugs actually under consideration.

AREAS COVERED

Recent findings on immunological mechanisms involved in the pathogenesis of the disease allowed us to identify several specific targets for biologic therapies. A systematic literature review was conducted between January 1997 and January 2020 on PubMed including national and international guidelines and recommendations, trials and case-control studies.

EXPERT OPINION

There is now a plethora of therapies that are directed against variable targets, and the physician has to choose the most appropriate available medication in order to achieve early and sustained remission with as few side effects as possible. Research is advancing very fast in order to be more and more specific in suppressing inflammatory pathways without harming natural defenses. Finally, pharmacoeconomic considerations will also be very important to deal with, considering the high cost of most of these molecules.

JAK inhibitors in refractory juvenile idiopathic arthritis-associated uveitis

To present our preliminary experience with JAK inhibitors in treating patients affected by juvenile idiopathic arthritis (JIA) and associated uveitis. Case series. Four consecutive patients with long-term history of juvenile idiopathic arthritis and severe associated uveitis were included in the study. Indication for treatment with JAK inhibitors was uncontrolled arthritis and/or uveitis despite different treatments with conventional and biologic disease modifying antirheumatic drugs (DMARDs). While on treatment with JAK inhibitors, namely, baricitinib (three cases) and tofacitinib (one case), all our patients showed improvement of uveitis defined as a reduction of intraocular inflammation according to Standardized Uveitis Nomenclature criteria. However, we observed a different response to treatment between the uveitis and the articular disease, as the latter did not respond as favorably as the former. Overall, the treatment was well tolerated by all patients and no ocular discomfort, ocular side effects, or allergic reactions were registered. JAK inhibitors may provide a new valuable treatment option in the therapeutic armamentarium for patients affected with JIA-associated uveitis, particularly in those refractory cases that are not adequately responding to conventional or biologic DMARDs.Key Points• A subset of patients with JIA uveitis either remain unresponsive or experience loss of efficacy• JAK inhibitors may provide a new valuable treatment option in JIA patients with uveitis• The safety profile was good with no occurrence of systemic side effects.

Roles of JAK2 in Aging, Inflammation, Hematopoiesis and Malignant Transformation

Clonal alterations in hematopoietic cells occur during aging and are often associated with the establishment of a subclinical inflammatory environment. Several age-related conditions and diseases may be initiated or promoted by these alterations. JAK2 mutations are among the most frequently mutated genes in blood cells during aging. The most common mutation within the JAK2 gene is JAK2-V617F that leads to constitutive activation of the kinase and thereby aberrant engagement of downstream signaling pathways. JAK2 mutations can act as central drivers of myeloproliferative neoplasia, a pre-leukemic and age-related malignancy. Likewise, hyperactive JAK-signaling is a hallmark of immune diseases and critically influences inflammation, coagulation and thrombosis. In this review we aim to summarize the current knowledge on JAK2 in clonal hematopoiesis during aging, the role of JAK-signaling in inflammation and lymphocyte biology and JAK2 function in age-related diseases and malignant transformation.

Janus kinase inhibitors in immuno-inflammatory rheumatic diseases: new opportunities and prospects

Despite the great success in the diagnosis and treatment of immuno-inflammatory rheumatic diseases (IIRD), which led to a significant improvement in the prognosis in many patients, the fundamental medical problems of this pathology – the restoration of quality of life and reduction of mortality to the population level – are far from solution. This served as a powerful impetus to the study of new approaches to pharmacotherapy of IIRD, one of which is associated with the use of low-molecular synthetic drugs that inhibit intracellular "signal" molecules-Janus kinase (JAK), the socalled Jakinibs. The current achievements and trends concerning the use of JAK inhibitors in the treatment of IIRD are considered.

Understanding Childhood Neuroimmune Diseases of the Central Nervous System

Immune-mediated diseases of the central nervous system (CNS) in childhood are a heterogeneous group of rare conditions sharing the inflammatory involvement of the CNS. This review highlights the growing knowledge of childhood neuroimmune diseases that primarily affect the CNS, outlining the clinical and diagnostic features, the pathobiological mechanisms and genetics, current treatment options, and emerging challenges. The clinical spectrum of these conditions is increasingly expanded, and the underlying mechanisms of dysregulation of the immune system could vary widely. Cell-mediated and antibody-mediated disorders, infection-triggered and paraneoplastic conditions, and genetically defined mechanisms can occur in previously healthy children and can contribute to different stages of the disease. The careful evaluation of the clinical presentation and temporal course of symptoms, the specific neuroimaging and immunological findings, and the exclusion of alternative causes are mandatory in clinical practice for the syndromic diagnosis. A common feature of these conditions is that immunotherapeutic agents could modulate the clinical course and outcomes of the disease. Furthermore, specific symptomatic treatments and comprehensive multidisciplinary care are needed in the overall management. We focus on recent advances on immune-mediated demyelinating CNS disorders, autoimmune encephalitis, interferonopathies, and possible neuroimmune disorders as Rasmussen encephalitis. Better knowledge of these conditions could allow prompt diagnosis and targeted immunotherapy, to decrease morbidity and mortality as well as to improve clinical outcomes, reducing the burden of the disease due to possible long-term neuropsychiatric sequelae. Persisting controversies remain in the rigorous characterization of each specific clinical entity because of the relative rarity in children; moreover, in a large proportion of suspected neuroimmune diseases, the immune "signature" remains unidentified; treatment guidelines are mostly based on retrospective cohort studies and expert opinions; then advances in specific molecular therapies are required. In the future, a better characterization of specific immunological biomarkers may provide a useful understanding of the underlying pathobiological mechanisms of these conditions in order to individualize more tailored therapeutic options and paradigms. Multicenter collaborative research on homogeneous groups of patients who may undergo immunological studies and therapeutic trials could improve the characterization of the underlying mechanisms, the specific phenotypes, and tailored management.