Autoinflammatory granulomatous diseases: from Blau syndrome and early-onset sarcoidosis to NOD2-mediated disease and Crohn's disease

Genetic and immunological regulation of gut Microbiota: The Roles of TLRs, CLRs, and key proteins in microbial homeostasis and disease

The gut microbiota plays a crucial role in human health, influencing metabolism, immune regulation, and neurological function. This review examines the genetic and immunological mechanisms governing microbiota composition, with a focus on key pattern recognition receptors, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), and signaling proteins such as CARD9 and NOD2. We discuss how genetic polymorphisms in these receptors contribute to gut dysbiosis and disease susceptibility, particularly in inflammatory bowel disease (IBD) and neurodegenerative disorders like Parkinson's disease. Additionally, we explore emerging microbiota-targeted therapeutic strategies, including probiotics and precision medicine approaches. By synthesizing recent advancements, this review examines how genetic and immunological mechanisms regulate gut microbiota and influence disease susceptibility, emphasizing key therapeutic implications.

NOD2 promotes sepsis-induced neuroinflammation by increasing brain endoplasmic reticulum stress mediated by LACC1

BACKGROUND

Although nucleotide-binding oligomerization domain-containing protein 2 (NOD2) has been associated with diverse inflammatory states and some neurological diseases, its role in regulating sepsis-induced neuroinflammation remains unexplored. This study aimed to determine the role of NOD2 in modulating sepsis-induced neuroinflammation and to elucidate its potential mechanisms.

METHODS

mRNA and protein expression levels of NOD2 were measured in the periventricular white matter (PWM) of C57BL/6 mice and the microglia. NOD2-/- mice were generated using the CRISPR/Cas9 technology, and the septic mouse model was established by using cecal ligation puncture (CLP). Microglia were transfected with siRNA specific to NOD2 or laccase domain-containing protein 1 (LACC1) or treated with the endoplasmic reticulum stress (ER stress) inhibitor 4-phenylbutyrate (4-PBA) in vitro under muramyl dipeptide (MDP)-induced neuroinflammation. Immunofluorescence staining, Western blotting, and quantitative reverse transcription polymerase chain reaction were performed to evaluate neuroinflammation and ER stress. The ER structure was observed using transmission electron microscopy.

RESULTS

NOD2 expression level was upregulated in the mouse model of sepsis-induced neuroinflammation. The absence of NOD2 led to a protective effect against neuroinflammation, which was correlated with ER stress both in vitro and in vivo. LACC1 was identified as a notable mediator of ER stress, contributing to the exacerbation of neuroinflammation. Mechanistically, elevated NOD2 expression level promoted neuroinflammation by enhancing ER stress through LACC1. Notably, these effects were partially mitigated by LACC1 downregulation.

CONCLUSIONS

These findings highlight the pivotal role of NOD2 in promoting sepsis-induced neuroinflammation via regulating ER stress mediated by LACC1, and provide a new potential strategy for treating human neuroinflammation.

Yao Syndrome: An Overview of Genotypic Associations, Clinical Manifestations, Diagnosis, and Treatment

BACKGROUND

Yao syndrome (YAOS) is a rare systemic autoinflammatory disorder (AID) of the innate immune system. It was recently categorized as genetically transitional disease (GTD) and is associated with NOD2 variants located at multiple NOD2 gene loci. Unlike most other periodic fever syndromes, the estimated disease prevalence is 1-10/100,000 with a predominance for females and white adult population. In this review, we aimed to provide a detailed analysis of different aspects of this syndrome to help better understand the underlying pathogenesis and incorporate the current evidence-based medicine published to diagnose and manage these patients.

SUMMARY

We conducted literature search on YAOS from 2011 to 2024 using PubMed, Embase, and Scopus databases. Thirty-two studies were included in our narrative review. A descriptive analysis was performed of both Yao and non-Yao authored records to embrace the syndrome reported from all investigators and assess differences and similarities. The most reported gene variant is the homozygous IVS8+158 followed by compound heterozygous IVS8+158 and R702W. Mean age of disease onset is between 36 and 42 years. The mean age of disease diagnosis is between 40 and 45 years with a variable disease duration. Fever is the most commonly reported symptom followed by musculoskeletal, gastrointestinal symptoms and dermatitis. On laboratory workup, patients have elevated levels of erythrocyte sedimentation rate, C-reactive protein, and serum ferritin with negative autoantibody workup. Arthritic symptoms in YAOS patients have a positive response to sulfasalazine and glucocorticoids, while nonsteroidal anti-inflammatory drugs and colchicine produce minimal response. Anti-IL1 and anti-IL6 agents (canakinumab, anakinra, and tocilizumab) are effective treatment modalities.

KEY MESSAGES

The evolving concept and acceptance of GTD will hopefully further our understanding about this SAID and similar disorders. We suggest developing a registry of patients with YAOS to keep track of expanding data on this subject. It is important to understand various aspects of YAOS including genetic and environmental factors, differential diagnosis, clinical manifestations, laboratory findings, and treatment options available to diagnose and manage these patients appropriately and timely.

Proteomic Profiling of Tears in Blau Syndrome Patients in Identification of Potential Disease Biomarkers

Blau syndrome (BS) is a rare autoinflammatory granulomatosis characterized by granulomatous arthritis, uveitis, and dermatitis. Ocular complications are particularly severe in BS, significantly contributing to morbidity. This study aims to identify potential biomarkers for BS ocular degeneration through proteomic profiling of tear samples from affected patients. Seven subjects from the same family, including four carriers of the BS-associated NOD2 mutation (p.E383K), were recruited alongside healthy controls. Tear samples were collected using Schirmer strips and analyzed via mass spectrometry. A total of 387 proteins were identified, with significant differences in protein expression between BS patients, healthy familial subjects, and healthy controls. Key findings include the overexpression of alpha-2-macroglobulin (A2M) and immunoglobulin heavy constant gamma 4 (IGHG4) in BS patients. Bioinformatic analysis revealed that differentially expressed proteins are involved in acute-phase response, extracellular exosome formation, and protein binding. Notably, neutrophils' azurophilic granule components, as azurocidin (AZU1), myeloperoxidases (MPO), and defensins (DEFA3), were highly expressed in the most severely affected subject, suggesting a potential role of neutrophils in BS ocular severity. These proteins might be promising biomarkers for ocular involvement in BS, facilitating early detection and tailored treatment strategies.

Retrospective Single Nucleotide Polymorphism Analysis of Host Resistance and Susceptibility to Ovine Johne's Disease Using Restored FFPE DNA

Johne's disease (JD), also known as paratuberculosis, is a chronic, untreatable gastroenteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection. Evidence for host genetic resistance to disease progression exists, although it is limited due to the extended incubation period (years) and diagnostic challenges. To overcome this, previously restored formalin-fixed paraffin embedded tissue (FFPE) DNA from archived FFPE tissue cassettes was utilized for a novel retrospective case-control genome-wide association study (GWAS) on ovine JD. Samples from known MAP-infected flocks with ante- and postmortem diagnostic data were used. Cases (N = 9) had evidence of tissue infection, compared to controls (N = 25) without evidence of tissue infection despite positive antemortem diagnostics. A genome-wide efficient mixed model analysis (GEMMA) to conduct a GWAS using restored FFPE DNA SNP results from the Illumina Ovine SNP50 Bead Chip, identified 10 SNPs reaching genome-wide significance of p < 1 × 10-6 on chromosomes 1, 3, 4, 24, and 26. Pathway analysis using PANTHER and the Kyoto Encyclopedia of Genes and Genomes (KEGG) was completed on 45 genes found within 1 Mb of significant SNPs. Our work provides a framework for the novel use of archived FFPE tissues for animal genetic studies in complex diseases and further evidence for a genetic association in JD.

Functional genomics in inborn errors of immunity

Inborn errors of immunity (IEI) comprise a diverse spectrum of 485 disorders as recognized by the International Union of Immunological Societies Committee on Inborn Error of Immunity in 2022. While IEI are monogenic by definition, they illuminate various pathways involved in the pathogenesis of polygenic immune dysregulation as in autoimmune or autoinflammatory syndromes, or in more common infectious diseases that may not have a significant genetic basis. Rapid improvement in genomic technologies has been the main driver of the accelerated rate of discovery of IEI and has led to the development of innovative treatment strategies. In this review, we will explore various facets of IEI, delving into the distinctions between PIDD and PIRD. We will examine how Mendelian inheritance patterns contribute to these disorders and discuss advancements in functional genomics that aid in characterizing new IEI. Additionally, we will explore how emerging genomic tools help to characterize new IEI as well as how they are paving the way for innovative treatment approaches for managing and potentially curing these complex immune conditions.

Identifying functional dysregulation of NOD2 variant Q902K in patients with Yao syndrome

BACKGROUND AND OBJECTIVES

The study investigated the pathogenesis of Yao syndrome (YAOS), a rare systemic autoinflammatory disease associated with the nucleotide-binding oligomerization domain containing 2 (NOD2) gene variants.

METHODS

RNA sequencing analyses were used to detect transcriptomic profile changes. Immunoblot and immunohistochemistry were used to examine the NOD2-mediated inflammatory signaling pathways and ELISA was used to detect cytokines.

RESULTS

Transcriptome analysis of YAOS revealed NOD-like receptor signaling pathway enrichment. Compared with HCs, P-RIP2, p-p65, p-p38, p-ERK, and p-JNK notably increased in PBMCs of a patient with YAOS. P-RIP2, p-p65, and p-p38 elevated in small intestinal mucosa tissues. P-p65 and p-p38 in synovial tissues from YAOS were higher than those in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Serum interleukin (IL)-6 level along with tumor necrosis factor (TNF)-α and IL-6 secreted from PBMCs were markedly higher in patients with YAOS in comparison to healthy controls (HCs). The supernatants of synovial cells from a patient with YAOS showed substantially higher IL-1β and IL-6 levels than those of RA and OA. Canakinumab therapy of a Q902K heterozygous patient with YAOS resulted in notable clinical improvement.

CONCLUSION

Overproduction of pro-inflammatory cytokines and the hyperactivation of NOD2-mediated signaling pathways were found in the NOD2 variant Q902K patient with YAOS. NOD2-RIP2-MAPK pathway might play a pivotal role in the pathogenesis of YAOS. These results provide new perspectives for targeted therapies in YAOS.

The effects of NOD-like receptors on adaptive immune responses

It has long been appreciated that cues from the innate immune system orchestrate downstream adaptive immune responses. Although previous work has focused on the roles of Toll-like receptors in this regard, relatively little is known about how Nod-like receptors instruct adaptive immunity. Here we review the functions of different members of the Nod-like receptor family in orchestrating effector and anamnestic adaptive immune responses. In particular, we address the ways in which inflammasome and non-inflammasome members of this family affect adaptive immunity under various infectious and environmental contexts. Furthermore, we identify several key mechanistic questions that studies in this field have left unaddressed. Our aim is to provide a framework through which immunologists in the adaptive immune field may view their questions through an innate-immune lens and vice-versa.

Vasculitis associated with adenosine deaminase 2 deficiency: at the crossroads between Behçet's disease and autoinflammation. A viewpoint

Adenosine deaminase 2 deficiency (DADA2) is a rare monogenic vasculopathy caused by loss-of-function homozygous or compound heterozygous mutations in ADA2, formerly CECR1 (cat eye syndrome chromosome region 1) gene. The DADA2 phenotype is widely heterogeneous, and patients may present with fever, weight loss, livedo reticularis/racemosa, digital ischemia, cutaneous ulceration, peripheral neuropathy, abdominal pain, bowel perforation, and portal or nephrogenic hypertension. More specific manifestations include early-onset ischemic or hemorrhagic stroke, mild immunodeficiency and hypogammaglobinemia, cytopenia, and vision disturbances. Herein, we present the case of a young male with vasculitis associated with DADA2. The presence of HLA-B51 and the clinical features of this patient raised the question of similarities between ADA2 deficiency, Behçet's disease, and NOD2-associated diseases. Treatment of this rare monogenic disease is challenging and based on small case series. The long-term experience of this patient proved the difficulties of prednisone tapering and the lack of satisfactory therapeutic strategies.

Blau syndrome with hypertension and hepatic granulomas: a case report and literature review

Background

Blau syndrome (BS) is a monogenic disorder caused by NOD2 gene variants characterized by the triad of granulomatous polyarthritis, rash, and uveitis. Atypical symptoms were recognized in one-third to one-half of individuals with BS. This study aims to describe the clinical features of BS patients with hypertension and digestive system involvement.

Methods

The complete clinical data of a BS patient complicated with hypertension and hepatic granulomas were collected and documented. We also performed a literature search to find all reported cases of BS with hypertension and digestive system involvement.

Results

We reported the case of a 19-year-old man who presented with early onset symmetric polyarthritis and hypertension at age 5 and hepatic granulomas and cirrhosis at age 19. He was diagnosed with BS by the finding of a variant of the NOD2 gene (R334W). Through the literature review, 24 patients with BS were found who were reported to have hypertension, and 38 patients were found who had different digestive system manifestations such as hepatic granulomas, hepatosplenomegaly, diverticulitis, and intestinal granuloma. Among the 38 BS patients with digestive system involvement, 14 had hepatic granulomas proven by liver biopsy.

Conclusions

Hypertension and digestive system involvement are rare manifestations of BS. Clinicians, especially rheumatologists, must be aware of atypical symptoms of BS.

Sarcoidosis, Mycobacterium paratuberculosis and Noncaseating Granulomas: Who Moved My Cheese

Clinical and histological similarities between sarcoidosis and tuberculosis have driven repeated investigations looking for a mycobacterial cause of sarcoidosis. Over 50 years ago, "anonymous mycobacteria" were suggested to have a role in the etiology of sarcoidosis. Both tuberculosis and sarcoidosis have a predilection for lung involvement, though each can be found in any area of the body. A key histopathologic feature of both sarcoidosis and tuberculosis is the granuloma-while the tuberculous caseating granuloma has an area of caseous necrosis with a cheesy consistency; the non-caseating granuloma of sarcoidosis does not have this feature. This article reviews and reiterates the complicity of the infectious agent, Mycobacterium avium subsp. paratuberculosis (MAP) as a cause of sarcoidosis. MAP is involved in a parallel story as the putative cause of Crohn's disease, another disease featuring noncaseating granulomas. MAP is a zoonotic agent infecting ruminant animals and is found in dairy products and in environmental contamination of water and air. Despite increasing evidence tying MAP to several human diseases, there is a continued resistance to embracing its pleiotropic roles. "Who Moved My Cheese" is a simple yet powerful book that explores the ways in which individuals react to change. Extending the metaphor, the "non-cheesy" granuloma of sarcoidosis actually contains the difficult-to-detect "cheese", MAP; MAP did not move, it was there all along.

Play the plug: How bacteria modify recognition by host receptors?

The diverse microbial community that colonizes the gastrointestinal tract has remarkable effects on the host immune system and physiology resulting in homeostasis or disease. In both scenarios, the gut microbiota interacts with their host through ligand-receptor binding whereby the downstream signaling processes determine the outcome of the interaction as disease or the counteractive immune responses of the host. Despite several studies on microbe-host interactions and the mechanisms by which this intricate process happens, a comprehensive and updated inventory of known ligand-receptor interactions and their roles in disease is paramount. The ligands which originate as a result of microbial responses to the host environment contribute to either symbiotic or parasitic relationships. On the other hand, the host receptors counteract the ligand actions by mounting a neutral or an innate response. The varying degrees of polymorphic changes in the host receptors contribute to specificity of interaction with the microbial ligands. Additionally, pathogenic microbes manipulate host receptors with endogenous enzymes belonging to the effector protein family. This review focuses on the diversity and similarity in the gut microbiome-host interactions both in health and disease conditions. It thus establishes an overview that can help identify potential therapeutic targets in response to critically soaring antimicrobial resistance as juxtaposed to tardy antibiotic development research.

Selective autophagy of RIPosomes maintains innate immune homeostasis during bacterial infection

The NOD1/2-RIPK2 is a key cytosolic signaling complex that activates NF-κB pro-inflammatory response against invading pathogens. However, uncontrolled NF-κB signaling can cause tissue damage leading to chronic diseases. The mechanisms by which the NODs-RIPK2-NF-κB innate immune axis is activated and resolved remain poorly understood. Here, we demonstrate that bacterial infection induces the formation of endogenous RIPK2 oligomers (RIPosomes) that are self-assembling entities that coat the bacteria to induce NF-κB response. Next, we show that autophagy proteins IRGM and p62/SQSTM1 physically interact with NOD1/2, RIPK2 and RIPosomes to promote their selective autophagy and limit NF-κB activation. IRGM suppresses RIPK2-dependent pro-inflammatory programs induced by Shigella and Salmonella. Consistently, the therapeutic inhibition of RIPK2 ameliorates Shigella infection- and DSS-induced gut inflammation in Irgm1 KO mice. This study identifies a unique mechanism where the innate immune proteins and autophagy machinery are recruited together to the bacteria for defense as well as for maintaining immune homeostasis.

Incomplete penetrance of NOD2 C483W mutation underlining Blau syndrome

BACKGROUND

Blau syndrome (BS) is a rare autoinflammatory disorder with NOD2 gain-of-function mutation and characterized by autoactivation of the NFκB pathway. Classically considered a disease of high penetrance, reports on NOD2 mutations underlining BS with incomplete penetrance is limited.

CASE PRESENTATION

The proband is a 9-year-old girl presented with brownish annular infiltrative plaques and symmetric boggy polyarthritis over bilateral wrists and ankles. Her skin biopsy revealed noncaseating granulomas inflammation with multinucleated giant cells. A novel C483W NOD2 mutation was identify in the proband and her asymptomatic father. Functional examinations including autoactivation of the NFκB pathway demonstrated by in vitro HEK293T NOD2 overexpression test as well as intracellular staining of phosphorylated-NFκB in patient's CD11b⁺ cells were consistent with BS.

CONCLUSIONS

We reported a novel C483W NOD2 mutation underlining BS with incomplete penetrance. Moreover, a phosphorylated-NFκB intracellular staining assay of CD11b⁺ was proposed to assist functional evaluation of NFκB autoactivation in patient with BS.

NOD1, NOD2, and NLRC5 Receptors in Antiviral and Antimycobacterial Immunity

The innate immune system recognizes pathogen-associated molecular motifs through pattern recognition receptors (PRRs) that induce inflammasome assembly in macrophages and trigger signal transduction pathways, thereby leading to the transcription of inflammatory cytokine genes. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) represent a family of cytosolic PRRs involved in the detection of intracellular pathogens such as mycobacteria or viruses. In this review, we discuss the role of NOD1, NOD2, and NLRC5 receptors in regulating antiviral and antimycobacterial immune responses by providing insight into molecular mechanisms as well as their potential health and disease implications.

Interstitial lung diseases

Over 200 interstitial lung diseases, from ultra rare to relatively common, are recognised. Most interstitial lung diseases are characterised by inflammation or fibrosis within the interstitial space, the primary consequence of which is impaired gas exchange, resulting in breathlessness, diminished exercise tolerance, and decreased quality of life. Outcomes vary considerably for each of the different interstitial lung diseases. In some conditions, spontaneous reversibility or stabilisation can occur, but unfortunately in many people with interstitial lung disease, especially in those manifesting progressive pulmonary fibrosis, respiratory failure and death are a sad reality. Over the past 3 years, the field of interstitial lung disease has had important advances, with the approval of drugs to treat systemic sclerosis-associated interstitial lung disease, interstitial lung disease-associated pulmonary hypertension, and different forms of progressive pulmonary fibrosis. This Seminar provides an update on epidemiology, pathogenesis, presentation, diagnosis, disease course, and management of the interstitial lung diseases that are most frequently encountered in clinical practice. Furthermore, we describe how developments have led to a shift in the classification and treatment of interstitial lung diseases that exhibit progressive pulmonary fibrosis and summarise the latest practice-changing guidelines. We conclude with an outline of controversies, uncertainties, and future directions.

Identification of variants in genes associated with autoinflammatory disorders in a cohort of patients with psoriatic arthritis

Objectives

Besides adaptive immunity genes, genetic risk factors for psoriatic arthritis (PsA) include innate immunity loci, which suggests an autoinflammatory disease mechanism, at least in a subset of patients. Here, we aimed at investigating the autoinflammatory genetic background of PsA.

Methods

A total of 120 patients with PsA visiting the outpatient clinics of the Hannover University hospital underwent targeted next-generation sequencing, searching for variations in genes linked with inborn errors of immunity classified as autoinflammatory disorders (AIDs). Deleteriousness of rare variants was evaluated through in silico analysis.

Results

We found 45 rare predicted deleterious variants in 37 out of 120 (30.8%) patients with PsA. Relatively common were variants in AP1S3, PLCG2, NOD2 and NLRP12. All 45 variants were monoallelic and 25 of them, identified in 20 out of 120 (16.7%) patients, were localised in genes associated with autosomal dominant (AD) disorders. Detection of those variants is associated with pustular psoriasis or a coexisting inflammatory bowel disease (IBD).

Conclusions

Approximately 30% of patients with PsA harboured at least one variant in a gene associated with an AID, suggesting an autoinflammatory disease mechanism. Detection of variants in genes linked to AD-AIDs may explain extra-articular manifestations of PsA, such as pustular psoriasis and IBD.

Association of rare variants in genes of immune regulation with pediatric autoimmune CNS diseases

Background

There is a gap in the literature regarding genetic underpinnings of pediatric autoimmune CNS diseases. This study explored rare gene variants implicated in immune dysregulation within these disorders.

Methods

This was a single-center observational study of children with inflammatory CNS disorder who had genetic testing through next generation focused exome sequencing targeting 155 genes associated with innate or adaptive immunity. For in silico prediction of functional effects of single-nucleotide variants, Polymorphism Phenotyping v2, and Sorting Intolerant from Tolerant were used, and Combined Annotation Dependent Depletion (CADD) scores were calculated. Identified genes were analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Results

Of 54 patients, 42 (77.8%) carried variant(s), among which 12 (22.2%) had 3–8 variants. Eighty-eight unique single-nucleotide variants of 55 genes were identified. The most variants were detected in UNC13D, LRBA, LYST, NOD2, DOCK8, RNASEH2A, STAT5B, and AIRE. The majority of variants (62, 70.4%) had CADD > 10. KEGG pathway analysis revealed seven genes associated with primary immunodeficiency (Benjamini 1.40E − 06), six genes with NOD-like receptor signaling (Benjamini 4.10E − 04), five genes with Inflammatory Bowel Disease (Benjamini 9.80E − 03), and five genes with NF-kappa B signaling pathway (Benjamini 1.90E − 02).

Discussion

We observed a high rate of identification of rare and low-frequency variants in immune regulatory genes in pediatric neuroinflammatory CNS disorders. We identified 88 unique single-nucleotide variants of 55 genes with pathway analysis revealing an enrichment of NOD2-receptor signaling, consistent with involvement of the pathway within other autoinflammatory conditions and warranting further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11325-2.

Regulation of Immune Homeostasis via Muramyl Peptides-Low Molecular Weight Bioregulators of Bacterial Origin

Metabolites and fragments of bacterial cells play an important role in the formation of immune homeostasis. Formed in the course of evolution, symbiotic relationships between microorganisms and a macroorganism are manifested, in particular, in the regulation of numerous physiological functions of the human body by the innate immunity receptors. Low molecular weight bioregulators of bacterial origin have recently attracted more and more attention as drugs in the prevention and composition of complex therapy for a wide range of diseases of bacterial and viral etiology. Signaling networks show cascades of causal relationships of deterministic phenomena that support the homeostasis of multicellular organisms at different levels. To create networks, data from numerous biomedical and clinical research databases were used to prepare expert systems for use in pharmacological and biomedical research with an emphasis on muramyl dipeptides. Muramyl peptides are the fragments of the cell wall of Gram-positive and Gram-negative bacteria. Binding of muramyl peptides with intracellular NOD2 receptors is crucial for an immune response on pathogens. Depending on the microenvironment and duration of action, muramyl peptides possess positive or negative regulation of inflammation. Other factors, such as genetic, pollutions, method of application and stress also contribute and should be taken into account. A system biology approach should be used in order to systemize all experimental data for rigorous analysis, with the aim of understanding intrinsic pathways of homeostasis, in order to define precise medicine therapy and drug design.

Monogenic disorders as mimics of juvenile idiopathic arthritis

BACKGROUND

Juvenile idiopathic arthritis is the most common chronic rheumatic disease of childhood. The term JIA encompasses a heterogenous group of diseases. The variability in phenotype of patients affected by the disease means it is not uncommon for mimics of JIA to be misdiagnosed.

CASE PRESENTATION

We present four cases who were treated in single tertiary rheumatology centre for JIA who were subsequently diagnosed with a rare monogenic disease. All four patients shared the unifying features of presenting in early childhood and subsequently suffered with refractory disease, not amenable to usual standards of treatment. Multicentric Carpotarsal Osteolysis Syndrome and Camptodactyly-arthropathy-coxa vara-pericarditis syndrome are non-inflammatory conditions and patients typically present with arthropathy, normal inflammatory markers and atypical radiological features. Blau syndrome is an autosomal dominant condition and patients will typically have symmetrical joint involvement with a strong family history of arthritis, signifying the genetic aetiology.

CONCLUSIONS

We share our learning from these cases to add to the growing portfolio of JIA mimics and to highlight when to consider an alternative diagnosis. In cases of refractory disease and diagnostic uncertainty further imaging and genetic testing can play a crucial role in establishing the aetiology. In all of these cases the correct diagnosis was made due to careful, longitudinal clinical phenotyping and a close working relationship between rheumatology, radiology and clinical genetics; highlighting the importance of the multidisciplinary team in managing complex patients.

Potential Composite Digenic Contribution of NPC1 and NOD2 Leading to Atypical Lethal Niemann-Pick Type C with Initial Crohn’s Disease-like Presentation: Genotype-Phenotype Correlation Study

Niemann–Pick disease type C (NPC) is an autosomal recessive neurovisceral disease characterized by progressive neurodegeneration with variable involvement of multisystemic abnormalities. Crohn’s disease (CD) is an inflammatory bowel disease (IBD) with a multifactorial etiology influenced by variants in NOD2. Here, we investigated a patient with plausible multisystemic overlapping manifestations of both NPC and CD. Her initial hospitalization was due to a prolonged fever and non-bloody diarrhea. A few months later, she presented with recurrent skin tags and anal fissures. Later, her neurological and pulmonary systems progressively deteriorated, leading to her death at the age of three and a half years. Differential diagnosis of her disease encompassed a battery of clinical testing and genetic investigations. The patient’s clinical diagnosis was inconclusive. Specifically, the histopathological findings were directed towards an IBD disease. Nevertheless, the diagnosis of IBD was not consistent with the patient’s subsequent neurological and pulmonary deterioration. Consequently, we utilized a genetic analysis approach to guide the diagnosis of this vague condition. Our phenotype–genotype association attempts led to the identification of candidate disease-causing variants in both NOD2 and NPC1. In this study, we propose a potential composite digenic impact of these two genes as the underlying molecular etiology. This work lays the foundation for future functional and mechanistic studies to unravel the digenic role of NOD2 and NPC1.

Progress in the genetics of uveitis

Uveitis is the most common form of intraocular inflammatory disease and is a significant cause of visual impairment worldwide. Aetiologically, uveitis can also be classified into infectious uveitis and non-infectious uveitis. The common non-infectious forms of uveitis include acute anterior uveitis (AAU), Behçet’s disease (BD), Vogt-Koyanagi-Harada (VKH) disease, birdshot chorioretinopathy (BSCR), sarcoid uveitis. In addition, a few monogenic autoinflammatory disorders can also cause uveitis, such as Blau Syndrome and haploinsufficiency of A20 (HA20). Although the exact pathogenesis of non-infectious uveitis is still unclear, it is well-recognised that it involves both genetic and environmental risk factors. A hallmark of uveitis is its strong associations with human leucocyte antigens (HLA). For examples, AAU, BD and BSCR are strongly associated with HLA-B27, HLA-B51, and HLA-A29, respectively. In uveitis studies, multiple GWAS have successfully been conducted and led to identification of novel susceptibility loci, for example, IL23R has been identified in BD, VKH and AAU. In this review, we summarize the latest progress on the genetic associations of both HLA and non-HLA genes with major forms of uveitis, including AAU, BD, VKH, BSCR, sarcoid uveitis, Blau Syndrome and HA20, and potential future research directions.

Expression of Autoimmunity-Related Genes in Melanoma

Simple Summary

The present study selected four genes strongly related to autoimmunity. Their expression was found to be significantly altered in melanoma patients according to a multi-validation procedure carried out on 1948 patients. Such genes may represent suitable molecular targets to further investigate the role autoimmunity may play in melanoma setup and development. Our data suggest that autoimmunity may play a beneficial role in melanoma set up, at least to some extent.

Abstract

(1) Background. Immune response dysregulation plays a key role in melanoma, as suggested by the substantial prognosis improvement observed under immune-modulation therapy. Similarly, the role of autoimmunity is under large investigation in melanoma and other cancers. (2) Methods. Expression of 98 autoimmunity-related genes was investigated in 1948 individuals (1024 melanoma and 924 healthy controls). Data were derived from four independent databases, namely, GEO in the selection phase, and Ist Online, GEPIA2 and GENT2, in three sequential validation-steps. ROC analyses were performed to measure the ability to discriminate melanoma from controls. Principal Component Analysis (PCA) was used to combine expression data; survival analysis was carried out on the GEPIA2 platform. (3) Results. Expression levels of NOD2, BAX, IL-18 and ADRB2 were found to be significantly different in melanoma vs. controls and discriminate melanoma from controls in an extremely effective way, either as single molecules (AUC > 0.93 in all cases) or as a profile, according to the PCA analysis. Patients showing high-expression of NOD2 and of IL-18 also show a significant survival improvement as compared to low-expression patients. (4) Conclusions. Four genes strongly related to autoimmunity show a significant altered expression in melanoma samples, highlighting the role they may play in melanoma.

Expansion of Phenotypic and Genotypic Spectrum in Yao Syndrome: A Case Series

OBJECTIVES

Yao syndrome (YAOS; OMIM 617321) was formerly termed nucleotide-binding oligomerization domain-containing protein 2 (NOD2)-associated autoinflammatory disease. This study sought to report novel findings related to this disease.

METHODS

A medical records review analysis of a case series was conducted, and all patients fulfilled the diagnostic criteria for YAOS and underwent comprehensive diagnostic workups, including molecular genotyping of blood specimens for periodic fever syndromes and NOD2-associated disease.

RESULTS

A total of 11 patients with YAOS were analyzed, and all were Whites with a median age of 25.9 years at disease onset. All patients shared the similar autoinflammatory phenotype of YAOS. Among the 11 patients, we identified 7 patients who had the known phenotype of YAOS, as well as recurring and brief eyelid swelling with or without eyelid discoloration or conjunctivitis. Molecular analysis of blood cells using periodic fever gene panel has identified the presence of NOD2 variants in all 11 patients. Apart from the known YAOS-associated common NOD2 genotype, 5 novel and unknown significance NOD2 variants were identified in patients who presented with typical phenotype of YAOS.

CONCLUSIONS

This study provides novel clinical and molecular data for YAOS and supports the expansion of the phenotypic and genotypic spectrum of the disease.

Blau Syndrome Complicated by Atypical Type IIa Takayasu Arteritis

Blau syndrome (BS) is a rare, autosomal dominant monogenic autoinflammatory disease, usually presenting as a triad of symptoms (granulomatous dermatitis, uveitis, and nonerosive arthritis) and caused by gain-of-function mutations in the nucleotide oligomerization domain 2 (NOD2) gene. However, very few reports in children of copresence of BS with large vessel vasculitis exist. We hereby describe a case of BS associated with clinical features of Takayasu arteritis. An 8.5-year-old boy presented with hypertension, cardiac insufficiency, arthritis, and ocular disease. Among other investigations, he underwent cervical and chest computed tomography and computed tomography angiography scans that revealed the presence of type IIa Takayasu arteritis lesions. Genetic analysis revealed a heterozygous mutation of NOD2 gene leading to the amino acid exchange Arg-587-Cys in the NACHT domain of the NOD2 protein (R587C) as pathogenic cause of BS. He received treatment with prednisolone, methotrexate, and infliximab (antitumor necrosis factor-α) in addition to antihypertensive medication with a favorable clinical response. Cases of BS should be investigated for the coexistence of Takayasu arteritis. However, further research is required to delineate a possible common pathogenic mechanism between the two clinical entities.

Uveitis in Children and Adolescents

Childhood noninfectious uveitis leads to sight-threatening complications. Idiopathic chronic anterior uveitis and juvenile idiopathic arthritis-associated uveitis are most common. Inflammation arises from an immune response against antigens within the eye. Ophthalmic work-up evaluates anatomic involvement, disease activity, ocular complications, and disease course. Local and/or systemic glucocorticoids are initial treatment, but not as long-term sole therapy to avoid glucocorticoids-induced toxicity or persistent ocular inflammation. Children with recurrent, refractory, or severe disease require systemic immunosuppression with methotrexate and/or anti-tumor necrosis factor monoclonal antibody medications (adalimumab, infliximab). Goals of early detection and treatment are to optimize vision in childhood uveitis.

A solid-phase approach for the synthesis of muramyl dipeptide conjugates for detection of NOD2

Proper recognition of invading pathogens and prompt initiation of host defense mechanisms are instrumental for the maintenance of organismal homeostasis. Nucleotide-binding oligomerization domain-containing (NOD)-like receptors (NLRs) serve as pathogen-recognition receptors that specifically recognize bacterial peptidoglycans. NOD2 detects muramyl dipeptide (MDP) through its carboxy-terminal leucine rich repeats (LRRs), which enables the activation of downstream inflammatory signaling. Synthesis of MDP conjugates based on solution phase chemistry have been previously reported. Our solid phase approach synthetically provides a facile approach for the conjugation of biological probes to MDP, with the advantage of minimal functional/protecting group manipulation, and reduction in the laborious process of intermediate purification and isolation. MDP conjugates that we generated using solid phase synthesis allow detection of NOD2 is cell lysates and NOD2 subcellular localization by immunofluorescence microscopy. MDP-PEG6-Cyanine5.5 conjugate selectively colocalized with WT NOD2 but not NOD2 variant found in Crohn's disease, which lacks carboxy-terminal end and cannot bind MDP. Overall, these data indicate that distinct solid phase-produced MDP conjugates can be used to examine biological properties of NOD2 and could potentially facilitate further development of NOD2 targeting agents.

NF-κB: At the Borders of Autoimmunity and Inflammation

The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory response. In the first part of this review, we discuss the NF-κB inducers, signaling pathways, and regulators involved in immune homeostasis as well as detail the importance of post-translational regulation by ubiquitination in NF-κB function. We also indicate the stages of central and peripheral tolerance where NF-κB plays a fundamental role. With respect to central tolerance, we detail how NF-κB regulates medullary thymic epithelial cell (mTEC) development, homeostasis, and function. Moreover, we elaborate on its role in the migration of double-positive (DP) thymocytes from the thymic cortex to the medulla. With respect to peripheral tolerance, we outline how NF-κB contributes to the inactivation and destruction of autoreactive T and B lymphocytes as well as the differentiation of CD4⁺-T cell subsets that are implicated in immune tolerance. In the latter half of the review, we describe the contribution of NF-κB to the pathogenesis of autoimmunity and autoinflammation. The recent discovery of mutations involving components of the pathway has both deepened our understanding of autoimmune disease and informed new therapeutic approaches to treat these illnesses.

The combined prevalence of classified rare rheumatic diseases is almost double that of ankylosing spondylitis

BACKGROUND

Rare diseases (RDs) affect less than 5/10,000 people in Europe and fewer than 200,000 individuals in the United States. In rheumatology, RDs are heterogeneous and lack systemic classification. Clinical courses involve a variety of diverse symptoms, and patients may be misdiagnosed and not receive appropriate treatment. The objective of this study was to identify and classify some of the most important RDs in rheumatology. We also attempted to determine their combined prevalence to more precisely define this area of rheumatology and increase awareness of RDs in healthcare systems. We conducted a comprehensive literature search and analyzed each disease for the specified criteria, such as clinical symptoms, treatment regimens, prognoses, and point prevalences. If no epidemiological data were available, we estimated the prevalence as 1/1,000,000. The total point prevalence for all RDs in rheumatology was estimated as the sum of the individually determined prevalences.

RESULTS

A total of 76 syndromes and diseases were identified, including vasculitis/vasculopathy (n = 15), arthritis/arthropathy (n = 11), autoinflammatory syndromes (n = 11), myositis (n = 9), bone disorders (n = 11), connective tissue diseases (n = 8), overgrowth syndromes (n = 3), and others (n = 8). Out of the 76 diseases, 61 (80%) are classified as chronic, with a remitting-relapsing course in 27 cases (35%) upon adequate treatment. Another 34 (45%) diseases were predominantly progressive and difficult to control. Corticosteroids are a therapeutic option in 49 (64%) syndromes. Mortality is variable and could not be determined precisely. Epidemiological studies and prevalence data were available for 33 syndromes and diseases. For an additional eight diseases, only incidence data were accessible. The summed prevalence of all RDs was 28.8/10,000.

CONCLUSIONS

RDs in rheumatology are frequently chronic, progressive, and present variable symptoms. Treatment options are often restricted to corticosteroids, presumably because of the scarcity of randomized controlled trials. The estimated combined prevalence is significant and almost double that of ankylosing spondylitis (18/10,000). Thus, healthcare systems should assign RDs similar importance as any other common disease in rheumatology.

Challenging Mimickers in the Diagnosis of Sarcoidosis: A Case Study

Sarcoidosis is a systemic granulomatous disease of unknown cause characterized by a wide variety of presentations. Its diagnosis is based on three major criteria: a clinical presentation compatible with sarcoidosis, the presence of non-necrotizing granulomatous inflammation in one or more tissue samples, and the exclusion of alternative causes of granulomatous disease. Many conditions may mimic a sarcoid-like granulomatous reaction. These conditions include infections, neoplasms, immunodeficiencies, and drug-induced diseases. Moreover, patients with sarcoidosis are at risk of developing opportunistic infections or lymphoma. Reliably confirming the diagnosis of sarcoidosis and better identifying new events are major clinical problems in daily practice. To address such issues, we present seven emblematic cases, seen in our department, over a ten-year period along with a literature review about case reports of conditions misdiagnosed as sarcoidosis.

Cellular stress promotes NOD1/2-dependent inflammation via the endogenous metabolite sphingosine-1-phosphate

Cellular stress has been associated with inflammation, yet precise underlying mechanisms remain elusive. In this study, various unrelated stress inducers were employed to screen for sensors linking altered cellular homeostasis and inflammation. We identified the intracellular pattern recognition receptors NOD1/2, which sense bacterial peptidoglycans, as general stress sensors detecting perturbations of cellular homeostasis. NOD1/2 activation upon such perturbations required generation of the endogenous metabolite sphingosine-1-phosphate (S1P). Unlike peptidoglycan sensing via the leucine-rich repeats domain, cytosolic S1P directly bound to the nucleotide binding domains of NOD1/2, triggering NF-κB activation and inflammatory responses. In sum, we unveiled a hitherto unknown role of NOD1/2 in surveillance of cellular homeostasis through sensing of the cytosolic metabolite S1P. We propose S1P, an endogenous metabolite, as a novel NOD1/2 activator and NOD1/2 as molecular hubs integrating bacterial and metabolic cues.

Histologic Patterns and Clues to Autoinflammatory Diseases in Children: What a Cutaneous Biopsy Can Tell Us

Autoinflammation is defined by aberrant, antigen-independent activation of the innate immune signaling pathways. This leads to increased, pro-inflammatory cytokine expression and subsequent inflammation. In contrast, autoimmune and allergic diseases are antigen-directed immune responses from activation of the adaptive immune system. The innate and adaptive immune signaling pathways are closely interconnected. The group of 'complex multigenic diseases' are a result of mutual dysregulation of both the autoinflammatory and autoimmune physiologic components. In contrast, monogenic autoinflammatory syndromes (MAIS) result from single mutations and are exclusively autoinflammatory in their pathogenesis. Studying the clinical and histopathological findings for the various MAIS explains the phenotypical correlates of their specific mutations. This review aims to group the histopathologic clues for autoinflammation into three recognizable patterns. The presence of these histologic patterns in a pediatric patient with recurrent fevers and systemic inflammation should raise suspicion of an autoinflammatory component in MAIS, or, more frequently, in a complex multigenic disease. The three major histopathological patterns seen in autoinflammation are as follows: (i) the 'neutrophilic' pattern, seen in urticarial neutrophilic dermatosis, pustular psoriasis, aseptic neutrophilic folliculitis, and Sweet's syndrome; (ii) the 'vasculitic' pattern seen in small vessel-vasculitis (including hypersensitivity/leukocytoclastic vasculitis, thrombosing microangiopathy and lymphocytic vasculitis), and intermediate-sized vessel vasculitis, mimicking polyarteritis nodosa; and (iii) the 'granulomatous' pattern. Beyond these three patterns, there are additional histopathologic clues, which are detailed below. It is important for a dermatopathologist to recognize the patterns of autoinflammation, so that a diagnosis of MAIS or complex multigenic diseases may be obtained. Finally, careful histopathologic analyses could contribute to a better understanding of the various clinical manifestations of autoinflammation.

NOD2 Mutation-Associated Case with Blau Syndrome Triggered by BCG Vaccination

We describe a patient who developed multiple granulomatous skin lesions after Bacille de Calmette et Guérin (BCG) vaccination without significant effect by topical corticosteroid, followed by painless cystic tumors on the bilateral knees and hands and inflammatory changes on ophthalmologic examination. A functional mutation in NOD2 was detected by a genetic analysis, and he was diagnosed as sporadic Blau syndrome. Since NOD2 acts as a sensor for the BCG component, it is possible that BCG vaccination may trigger granuloma formation in Blau syndrome patients with such genetic background.

Ubiquitination in the regulation of inflammatory cell death and cancer

The ubiquitin system is complex, multifaceted, and is crucial for the modulation of a vast number of cellular processes. Ubiquitination is tightly regulated at different levels by a range of enzymes including E1s, E2s, and E3s, and an array of DUBs. The UPS directs protein degradation through the proteasome, and regulates a wide array of cellular processes including transcription and epigenetic factors as well as key oncoproteins. Ubiquitination is key to the dynamic regulation of programmed cell death. Notably, the TNF signaling pathway is controlled by competing ubiquitin conjugation and deubiquitination, which governs both proteasomal degradation and signaling complex formation. In the inflammatory response, ubiquitination is capable of both activating and dampening inflammasome activation through the control of either protein stability, complex formation, or, in some cases, directly affecting receptor activity. In this review, we discuss the enzymes and targets in the ubiquitin system that regulate fundamental cellular processes regulating cell death, and inflammation, as well as disease consequences resulting from their dysregulation. Finally, we highlight several pre-clinical and clinical compounds that regulate ubiquitin system enzymes, with the aim of restoring homeostasis and ameliorating diseases.

Kinase inhibition in autoimmunity and inflammation

Despite recent advances in the treatment of autoimmune and inflammatory diseases, unmet medical needs in some areas still exist. One of the main therapeutic approaches to alleviate dysregulated inflammation has been to target the activity of kinases that regulate production of inflammatory mediators. Small-molecule kinase inhibitors have the potential for broad efficacy, convenience and tissue penetrance, and thus often offer important advantages over biologics. However, designing kinase inhibitors with target selectivity and minimal off-target effects can be challenging. Nevertheless, immense progress has been made in advancing kinase inhibitors with desirable drug-like properties into the clinic, including inhibitors of JAKs, IRAK4, RIPKs, BTK, SYK and TPL2. This Review will address the latest discoveries around kinase inhibitors with an emphasis on clinically validated autoimmunity and inflammatory pathways.

Immune modulating effects of receptor interacting protein 2 (RIP2) in autoinflammation and immunity

Receptor-interacting protein 2 (RIP2) is a kinase that is involved in downstream signaling of nuclear oligomerization domain (NOD)-like receptors NOD1 and 2 sensing bacterial peptidoglycans. RIP2-deficiency or targeting of RIP2 by pharmaceutical inhibitors partially ameliorates inflammatory diseases by reducing pro-inflammatory signaling in response to peptidoglycans. However, RIP2 is widely expressed and interacts with several other proteins suggesting additional functions outside the NOD-signaling pathway. In this review, we discuss the immunological functions of RIP2 and its possible role in autoinflammation and immunity.

ISSAID/EMQN Best Practice Guidelines for the Genetic Diagnosis of Monogenic Autoinflammatory Diseases in the Next-Generation Sequencing Era

BACKGROUND

Monogenic autoinflammatory diseases are caused by pathogenic variants in genes that regulate innate immune responses, and are characterized by sterile systemic inflammatory episodes. Since symptoms can overlap within this rapidly expanding disease category, accurate genetic diagnosis is of the utmost importance to initiate early inflammation-targeted treatment and prevent clinically significant or life-threatening complications. Initial recommendations for the genetic diagnosis of autoinflammatory diseases were limited to a gene-by-gene diagnosis strategy based on the Sanger method, and restricted to the 4 prototypic recurrent fevers (MEFV, MVK, TNFRSF1A, and NLRP3 genes). The development of best practices guidelines integrating critical recent discoveries has become essential.

METHODS

The preparatory steps included 2 online surveys and pathogenicity annotation of newly recommended genes. The current guidelines were drafted by European Molecular Genetics Quality Network members, then discussed by a panel of experts of the International Society for Systemic Autoinflammatory Diseases during a consensus meeting.

RESULTS

In these guidelines, we combine the diagnostic strength of next-generation sequencing and recommendations to 4 more recently identified genes (ADA2, NOD2, PSTPIP1, and TNFAIP3), nonclassical pathogenic genetic alterations, and atypical phenotypes. We present a referral-based decision tree for test scope and method (Sanger versus next-generation sequencing) and recommend on complementary explorations for mosaicism, copy-number variants, and gene dose. A genotype table based on the 5-category variant pathogenicity classification provides the clinical significance of prototypic genotypes per gene and disease.

CONCLUSIONS

These guidelines will orient and assist geneticists and health practitioners in providing up-to-date and appropriate diagnosis to their patients.

Ocular manifestations of Blau syndrome

PURPOSE OF REVIEW

This article summarizes the systemic and ocular manifestations of Blau syndrome, its genetic basis, and reviews recently published literature.

RECENT FINDINGS

A large multicenter prospective case series is underway, with 3-year preliminary results indicating the prevalence of uveitis, clinical characteristics and early data on its visual prognosis. Case reports have demonstrated the successful use of newer biologic agents.

SUMMARY

Blau syndrome is an exceedingly rare autoinflammatory disorder with skin, joint and eye manifestations. It is caused by autosomal dominant mutations of the NOD2 protein. Eye involvement is typically a chronic bilateral granulomatous iridocyclitis, often with multifocal choroiditis in the posterior segment. Treatment starts with topical and systemic steroids and often requires antimetabolites or biologic agents.

Regulation of Cell Death and Immunity by XIAP

X-chromosome-linked inhibitor of apoptosis protein (XIAP) controls cell survival in several regulated cell death pathways and coordinates a range of inflammatory signaling events. Initially identified as a caspase-binding protein, it was considered to be primarily involved in blocking apoptosis from both intrinsic as well as extrinsic triggers. However, XIAP also prevents TNF-mediated, receptor-interacting protein 3 (RIPK3)-dependent cell death, by controlling RIPK1 ubiquitylation and preventing inflammatory cell death. The identification of patients with germline mutations in XIAP (termed XLP-2 syndrome) pointed toward its role in inflammatory signaling. Indeed, XIAP also mediates nucleotide-binding oligomerization domain-containing 2 (NOD2) proinflammatory signaling by promoting RIPK2 ubiquitination within the NOD2 signaling complex leading to NF-κB and MAPK activation and production of inflammatory cytokines and chemokines. Overall, XIAP is a critical regulator of multiple cell death and inflammatory pathways making it an attractive drug target in tumors and inflammatory diseases.

Models Contribution to the Understanding of Sarcoidosis Pathogenesis: "Are There Good Models of Sarcoidosis?"

Sarcoidosis is a systemic, granulomatous, and noninfectious disease of unknown etiology. The clinical heterogeneity of the disease (targeted tissue(s), course of the disease, and therapy response) supports the idea that a multiplicity of trigger antigens may be involved. The pathogenesis of sarcoidosis is not yet completely understood, although in recent years, considerable efforts were put to develop novel experimental research models of sarcoidosis. In particular, sarcoidosis patient cells were used within in vitro 3D models to study their characteristics compared to control patients. Likewise, a series of transgenic mouse models were developed to highlight the role of particular signaling pathways in granuloma formation and persistence. The purpose of this review is to put in perspective the contributions of the most recent models in the understanding of sarcoidosis.

Monogenic autoinflammatory diseases in children: single center experience with clinical, genetic, and imaging review

Purpose

1. To review the contemporary literature and present a list of the imaging findings for patients with autoinflammatory diseases from our hospital. All these patients are found to have a genetic mutation that is responsible for their disease.

2. To present follow-up imaging findings, when available, and correlate those with symptoms and type of treatment administered in approximately 40 patients with autoinflammatory diseases of a single tertiary pediatric health care center including familial Mediterranean fever, Cryopyrin-associated autoinflammatory syndrome, PAPA (pyogenic arthritis, pyoderma gangrenousum, and acne) syndrome, and more. These findings are related to disease progression, treatment response, or treatment-induced changes.

Conclusion

Autoinflammatory diseases are relatively rare entities that can affect any system of the body. Given the many nonspecific imaging features, awareness of these diseases and good communication with clinicians aid in reaching an accurate diagnosis.

Whole-exome sequencing in three children with sporadic Blau syndrome, one of them co-presenting with recurrent polyserositis

Blau syndrome (BS) is a rare, chronic autoinflammatory disease with onset before age 4 and mainly characterised by granulomatous arthritis, recurrent uveitis, and skin rash. Sporadic (also known as early-onset sarcoidosis) or familial BS is caused by gain-of-function mutations in the NOD2 gene, which encodes for a multi-task protein that plays a crucial role in the innate immune defense. We report on three Mexican patients clinically diagnosed with BS who exhibited a likely pathogenic variant in NOD2 as revealed by whole-exome sequencing (WES) and Sanger sequencing: two variants (c.1000 C > T/p.Arg334Trp and c.1538 T > C/p.Met513Thr) lie in the ATP/Mg2+ binding site, whereas the other (c.3019dupC/p.Leu1007ProfsTer2) introduces a premature stop codon disrupting the last LRR domain (LRR9) formation; all three variants are consistent with gain-of-function changes. Interestingly, all these patients presented concomitant likely pathogenic variants in other inflammatory disease-related genes, i.e. TLR10, PRR12, MEFV and/or SLC22A5. Although the clinical presentation in these patients included the BS diagnostic triad, overall it was rather heterogeneous. It is plausible that this clinical variability depends partly on the patients' genetic background as suggested by our WES results. After this molecular diagnosis and given the absence of NOD2 mutations (demonstrated in two trios) and related symptoms in the respective parents (confirmed in all trios), patients 1 and 2 were considered to have sporadic BS, while patient 3, a sporadic BS-recurrent polyserositis compound phenotype. Altogether, our observations and findings underscore the overlapping among inflammatory diseases and the importance of determining the underlying genetic cause by high-throughput methods. Likewise, this study further reinforces a pathogenic link between the here found NOD2 variants and BS and envisages potential additive effects from other loci in these, and probably other patients.

Blau syndrome: a rare cause of exuberant granulomatous synovitis of the knee

Blau syndrome (BS) is a rare autosomal dominant familial granulomatous inflammatory disease presenting in early childhood with dermatitis, arthritis and uveitis. Early-onset sarcoidosis represents the sporadic form, and both are characterised by mutations in the CARD15/NOD2 gene on chromosome 16. We describe a 38-year-old man with known BS who presented for orthopaedic review following right-sided patellar dislocation. MRI of the injured knee demonstrated diffuse synovitis and prominent fatty tissue resembling lipoma arborescens with evidence of recent patellar dislocation. Synovectomy was performed and confirmed granulomatous synovitis. Knee imaging findings are described for the first time. Combining distinct morphological bone changes with synovitis which resembles lipoma arborescens and histology which includes sarcoidal-type granulomatous synovitis should lead the radiologist and pathologist to consider the diagnosis of BS.

Ophthalmological treatment of early-onset sarcoidosis/Blau syndrome in a Colombian child: A case report

Purpose

To report the ophthalmological approach of a patient with Blau syndrome (BS) in Colombia.

Observations

We describe a 9-year-old Colombian boy with sporadic BS due to a de novo nucleotide-binding oligomerization domain containing 2 (NOD2) mutation, who presented with joint and dermatologic symptoms. He was referred to the uveitis service with a single functional eye, due to retinal detachment in the other eye. Despite treatment with corticosteroids, methotrexate, and adalimumab, the patient continued to exhibit progressive disease.

Conclusion

BS-related uveitis is characterized by severe ocular morbidity. Appropriate interdisciplinary treatment is necessary for the correct identification and management of the disease, considering the inherent difficulty in its diagnosis due to its diverse clinical manifestations. The severity of BS-related uveitis in this report highlights the need for more effective therapies.

Sarcoidosis as an Autoimmune Disease

Despite the large number of performed studies, the etiology and pathogenesis of sarcoidosis still remain unknown. Most researchers allude to the possible autoimmune or immune-mediated genesis of the disease. This review attempts an integral analysis of currently available information suggesting an autoimmune genesis of sarcoidosis and is divided into four categories: the evaluation of clinical signs described both in patients with sarcoidosis and “classic” autoimmune diseases, the role of triggering factors in the development of sarcoidosis, the presence of immunogenic susceptibility in the development of the disease, and the analysis of cellular and humoral immune responses in sarcoidosis. Studying the etiology and pathogenesis of sarcoidosis will improve diagnostic procedures as well as the prognosis and patients' quality of life.

Expression and Role of Nucleotide-Binding Oligomerization Domain 2 (NOD2) in the Ocular Surface of Murine Dry Eye

Purpose

To investigate expression and role of nucleotide-binding oligomerization domain 2 (NOD2) in the ocular surface of experimental dry eye (EDE), which is a nod-like receptor member and is involved in innate immune response.

Methods

C57/BL6 female mice were divided into the groups: untreated (UT), EDE, and NOD2 knockout (KO) mice exposed to desiccating stress for 14 days. Clinical parameters and levels of inflammatory cytokine were measured at 3,5,7, and 14 days. Immunofluorescent staining for NOD2 and Western blot for RIP2 and NF-κB were performed at 14 days. Flow cytometry, PAS staining and TUNEL staining were performed.

Results

After EDE induction, NOD2 was expressed in the corneal epithelium of the EDE group. The EDE group showed a significantly increased RIP2 expression compared to the UT and NOD2-KO groups. A significantly lower expression of NF-κB and lower levels of IL-1β, IL-6, IFN-γ, and TNF-α were noted in the NOD2-KO group than in the EDE group. The NOD2-KO group had lower CD11b+ and CD4+CCR5+ T cells, TUNEL-positive cells and corneal staining score and higher density of conjunctival goblet cell density, tear volume, and tear film break-up time than the EDE group. The UT group showed significant differences in inflammatory and clinical parameters compared to the EDE and NOD2-KO groups.

Conclusions

The NOD2 receptor pathway induced inflammation and apoptosis by activation of RIP2 and NF-κB on the ocular surface of EDE, thereby reducing tear secretion. Therefore, NOD2 pathway may be involved in the pathogenesis of dry eye.