NOD2 gene–associated pediatric granulomatous arthritis: Clinical diversity, novel and recurrent mutations, and evidence of clinical improvement with interleukin-1 blockade in a Spanish cohort

A clinical guide to autoinflammatory diseases: familial Mediterranean fever and next-of-kin

Autoinflammatory diseases are associated with abnormal activation of the innate immune system, leading to clinical inflammation and high levels of acute-phase reactants. The first group to be identified was the periodic fever diseases, of which familial Mediterranean fever (FMF) is the most common. In FMF, genetic results are not always straightforward; thus, flowcharts to guide the physician in requesting mutation analyses and interpreting the findings are presented in this Review. The other periodic fever diseases, which include cryopyrin-associated periodic syndromes (CAPS), TNF receptor-associated periodic syndrome (TRAPS) and mevalonate kinase deficiency/hyperimmunoglobulin D syndrome (MKD/HIDS), have distinguishing features that should be sought for carefully during diagnosis. Among this group of diseases, increasing evidence exists for the efficacy of anti-IL-1 treatment, suggesting a major role of IL-1 in their pathogenesis. In the past decade, we have started to learn about the other rare autoinflammatory diseases in which fever is less pronounced. Among them are diseases manifesting with pyogenic lesions of the skin and bone; diseases associated with granulomatous lesions; diseases associated with psoriasis; and diseases associated with defects in the immunoproteasome. A better understanding of the pathogenesis of these autoinflammatory diseases has enabled us to provide targeted biologic treatment at least for some of these conditions.

Monogenic autoinflammatory diseases: disorders of amplified danger sensing and cytokine dysregulation

The pathogenesis of monogenic autoinflammatory diseases converges on the presence of exaggerated immune responses that are triggered through activation of altered pattern recognition receptor (PRR) pathways and result in cytokine/chemokine amplification loops and the inflammatory clinical phenotype seen in autoinflammatory patients. The PRR response can be triggered by accumulation of metabolites, by mutations in sensors leading to their constitutive overactivation, or by mutations in mediator cytokine pathways that lead to amplification and/or inability to downregulate an inflammatory response in hematopoietic and/or nonhematopoietic cells. The study of the pathogenesis of sterile inflammation in patients with autoinflammatory syndromes continues to uncover novel inflammatory pathways.

The Central Role of Anti-IL-1 Blockade in the Treatment of Monogenic and Multi-Factorial Autoinflammatory Diseases

Inherited autoinflammatory diseases are secondary to mutations of proteins playing a pivotal role in the regulation of the innate immunity leading to seemingly unprovoked episodes of inflammation. The understanding of the molecular pathways involved in these disorders has shed new lights on the pattern of activation and maintenance of the inflammatory response and disclosed new molecular therapeutic targets. Cryopyrin-associated periodic syndrome (CAPS) represents the prototype of an autoinflammatory disease. The study of the pathophysiological consequence of mutations in the cryopyrin gene (NLRP3) allowed the identification of intracellular pathways responsible for the activation and secretion of the potent inflammatory cytokine interleukin-1β (IL-1β). It became clear that several multi-factorial inflammatory conditions display a number of pathogenic and clinical similarities with inherited autoinflammatory diseases. The dramatic effect of interleukin-1 (IL-1) blockade in CAPS opened new perspectives for the treatment of other inherited and multi-factorial autoinflammatory disorders. Several IL-1 blockers are now available on the market. In this review we outline the more recent novelties in the treatment with different IL-1 blockers in inherited and multi-factorial autoinflammatory diseases.

Blau syndrome-associated uveitis and the NOD2 gene

Blau syndrome (BS), a rare autosomal dominant autoinflammatory syndrome, is an example of a monogenic disease. It was first described as a classic triad of uveitis, arthritis, and exanthema, typically seen in patients less than four years of age. Since that time, the phenotype has been expanded to include fever, cranial neuropathies, cardiovascular abnormalities, and granulomas of the liver and kidney. The ocular inflammation is often a panuveitis that occurs later in the disease course and typically carries the greatest morbidity in BS. BS has been mapped to the chromosomal region 16q12-21, also known as the NOD2 gene (formerly CARD15/NOD2). The disease is secondary to a single amino acid mutation NOD2 that leads to peptidoglycan-independent activity of nuclear factor (NF)-κB. Clinical and genetic aspects of BS will be discussed, as well as recent advances in treatment protocols.

Biological treatments: new weapons in the management of monogenic autoinflammatory disorders

Treatment of monogenic autoinflammatory disorders, an expanding group of hereditary diseases characterized by apparently unprovoked recurrent episodes of inflammation, without high-titre autoantibodies or antigen-specific T cells, has been revolutionized by the discovery that several of these conditions are caused by mutations in proteins involved in the mechanisms of innate immune response, including components of the inflammasome, cytokine receptors, receptor antagonists, and oversecretion of a network of proinflammatory molecules. Aim of this review is to synthesize the current experience and the most recent evidences about the therapeutic approach with biologic drugs in pediatric and adult patients with monogenic autoinflammatory disorders.

Clinical and transcriptional response to the long-acting interleukin-1 blocker canakinumab in Blau syndrome-related uveitis

OBJECTIVE

To report on the clinical response to canakinumab in a patient with sporadic nucleotide-binding oligomerization domain-containing protein 2 (NOD-2)-associated pediatric granulomatous arthritis (Blau syndrome) and severe resistant panuveitis, and to describe gene expression profile changes throughout such treatment.

METHODS

A 4-year-old boy was diagnosed as having Blau syndrome on the basis of typical clinical features, histologic evidence of noncaseating granulomas, and a NOD2 mutation. Ocular involvement was initially controlled by topical and oral corticosteroids, but over the years visual impairment and complications, such as macular edema and retinal detachment, progressed. Ocular disease remained persistently active despite treatment with multiple different immunosuppressants; therefore, canakinumab treatment was started. Before and during the first 6 months of treatment, the gene expression profile was determined each month.

RESULTS

Canakinumab treatment was well tolerated and led to rapid quiescence of uveitis, which had been continuously active before this treatment. Gene expression profiling analysis of the patient's blood prior to initiation of interleukin-1 (IL-1) blockade revealed differential expression of 1,993 transcripts when compared to healthy controls, and among the up-regulated transcripts, pathway analysis showed that the predominant network consisted of innate immunity-related transcripts. The transcriptional signature of the patient overlapped with the transcriptional signature of patients with systemic-onset juvenile idiopathic arthritis, and canakinumab treatment led to the normalization of most of these transcriptional changes.

CONCLUSION

The pathogenesis of Blau syndrome may be mediated by IL-1, and canakinumab may be useful when this disorder is unresponsive to more conventional treatments.

Monogenic autoinflammatory diseases: concept and clinical manifestations

The objective of this review is to describe the clinical manifestations of the growing spectrum of monogenic autoinflammatory diseases including recently described syndromes. The autoinflammatory diseases can be grouped based on clinical findings: 1. the three classic hereditary "periodic fever syndromes", familial Mediterranean Fever (FMF); TNF receptor associated periodic syndrome (TRAPS); and mevalonate kinase deficiency/hyperimmunoglobulinemia D and periodic fever syndrome (HIDS); 2. the cryopyrin associated periodic syndromes (CAPS), comprising familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) and neonatal-onset multisystem inflammatory disease (NOMID) or CINCA, and; 3. pediatric granulomatous arthritis (PGA); 4. disorders presenting with skin pustules, including deficiency of interleukin 1 receptor antagonist (DIRA); Majeed syndrome; pyogenic arthritis, pyoderma gangrenosum and acne (PAPA) syndrome; deficiency of interleukin 36 receptor antagonist (DITRA); CARD14 mediated psoriasis (CAMPS), and early-onset inflammatory bowel diseases (EO-IBD); 5. inflammatory disorders caused by mutations in proteasome components, the proteasome associated autoinflammatory syndromes (PRAAS) and 6. very rare conditions presenting with autoinflammation and immunodeficiency.

Autoinflammation: From monogenic syndromes to common skin diseases

Autoinflammation is characterized by aberrant regulation of the innate immune system and often manifests as periodic fevers and systemic inflammation involving multiple organs, including the skin. Mutations leading to abnormal behavior or activity of the interleukin 1 beta (IL-1ß)-processing inflammasome complex have been found in several rare autoinflammatory syndromes, for which anticytokine therapy such as IL-1 or tumor necrosis factor-alfa inhibition may be effective. It is becoming clear that features of autoinflammation also affect common dermatoses, some of which were previously thought to be solely autoimmune in origin (eg, vitiligo, systemic lupus erythematosus). Recognizing the pathogenetic role of autoinflammation can open up new avenues for the targeted treatment of complex, inflammatory dermatoses.

Nucleotide-binding oligomerization domain containing 2: structure, function, and diseases

OBJECTIVES

To systematically review literature about the structure and function of nucleotide-binding oligomerization domain containing 2 (NOD2) and its disease association.

METHODS

The English literature was searched using keywords "NOD2" and "disease". Relevant original and review articles were reviewed.

RESULTS

NOD2 is an intracellular protein and shares similar molecular structure with NOD1, pyrin, and cryopyrin. There are more than 100 NOD2 gene mutations, some of which have been linked to diseases such as Crohn disease, Blau syndrome, and NOD2-associated autoinflammatory disease (NAID). The NOD2 variants located in the leucine-rich repeat (LRR) region are susceptible to Crohn disease, and the variants in the nucleotide-binding domain (NBD) and in between the NBD and LRR are associated with Blau syndrome and NAID, respectively. No disease association with the gene variants has been found in rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, psoriasis/psoriatic arthritis, adult sarcoidosis, granulomatous polyangiitis, or multiple sclerosis. The potential association of the NOD2 variants with graft-versus-host-disease remains controversial. NOD2 functions mainly through RICK or RIP2 to activate p38 mitogen-activated protein kinases and NF-κB, resulting in inflammatory response, and enhanced autophagic activity. Biologic therapy may be beneficial for NOD2-associated diseases, and new drug development may be realized based upon the signaling pathways.

CONCLUSIONS

NOD2 gene mutations are associated with several diseases, and some of the mutations are of diagnostic value in Blau disease and NAID. To understand the NOD2 function, disease association, and its pathogenesis is important given the ever increasing clinical significance of NOD2.

Monogenic causes of inflammatory disease in rheumatology

PURPOSE OF REVIEW

To review the single-gene defects that can mimic rheumatologic diseases.

RECENT FINDINGS

Monogenic disorders can cause a variety of diseases that may be seen by a rheumatologist. Many of these illnesses present with recurrent episodes of arthritis, rash, fever and inflammation, and serositis. Recent discoveries have defined inflammatory diseases due to mutations in the IL-1 and IL-36 receptor antagonists, as well as the immunoproteosome. Further study of well defined monogenic causes of inflammatory diseases, such as FMF, PAPA, TRAPS, and HIDS, has elucidated the pathophysiology of these diseases leading to targeted immunotherapy with anticytokine biological medications.

SUMMARY

A rheumatologist should be aware of the genetic causes of inflammatory disease mimics. This will not only help with the prognosis of these diseases, but also help to guide therapy to prevent long-term complications associated with these disorders.

Systemic inflammatory and autoimmune disorders

Systemic disorders with possible involvement of the nervous system include a variety of diseases with presumed inflammatory and autoimmune pathomechanisms, among them Behçet disease, sarcoidosis, systemic lupus erythematosus, juvenile idiopathic arthritis, scleroderma, and Sjögren syndrome. This disease group encompasses systemic inflammatory disorders with a genetically defined dysregulation of the innate immune system as well as systemic autoimmune disorders characterized by alterations of the adaptive immunity such as autoantibodies and autoreactive T cells. Although more commonly diagnosed in adults, all of these diseases can manifest in childhood and some as early as infancy. Neurological involvement may represent the initial manifestation, and nearly every neurological symptom can be caused by inflammatory/autoimmune diseases. In a child with (sub)acute onset of otherwise unexplained neurological findings, consideration of inflammatory/autoimmune disorders may be of crucial therapeutic and prognostic importance. In the absence of disease-specific clinical features, the initial diagnostic workup is broad. Basic blood tests include inflammatory markers and autoantibodies. Cerebral magnetic resonance imaging and a lumbar puncture with measurement of opening pressure as well as cerebrospinal fluid analysis are indicated in most patients with central nervous system (CNS) involvement. Skin, muscle, or organ biopsies (e.g., renal) may provide additional information. Especially in patients with isolated CNS involvement, a brain biopsy may be indicated. Timely recognition and treatment of CNS inflammation may improve or even reverse clinical symptoms and prevent secondary brain injury.

Uveitis, the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT), and intravitreal biologics for ocular inflammation

PURPOSE

To provide perspective on the implications of the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT) on intravitreal biologic agents in uveitis and retinal diseases in which ocular inflammatory pathways are central to their pathogenesis.

DESIGN

Interpretative essay.

METHODS

Literature review and interpretation.

RESULTS

Besides the clear importance of CATT from a patient treatment perspective in age-related macular degeneration (AMD), these data highlight the critical relevance of highly specific protein immunotherapies offered with biologic agents. The CATT trial also provides a reminder regarding the importance of rigorous efficacy and safety monitoring required when administering intravitreal biologic therapy. Within the field of uveitis, systemic and local biologics have been used to effectively treat uveitis, targeting pathways implicated in both angiogenesis and inflammation (eg, tumor necrosis factor-α [TNF-α] and interleukin-2 pathways), and research on intravitreal biologic therapy for uveitis and AMD will continue to expand. With over 25 ongoing clinical trials on intravitreal biologic therapy for AMD, enthusiasm for vanguard biologic therapies should be tempered by judicious monitoring for adverse events.

CONCLUSION

The importance of the CATT trial encompasses day-to-day treatment decisions for AMD, as well as lessons on how biologics for ocular disease should be implemented into clinical practice. Specifically, the introduction of intravitreal biologic therapies into clinical practice for uveitis, AMD, and other ocular diseases in which inflammation is involved should be guided by a clear understanding of the immunotherapeutic agent and its molecular target and with rigorous monitoring for both patient benefit and patient safety.

Ocular manifestations of the autoinflammatory syndromes

The autoinflammatory syndromes are rare inherited disorders characterized by recurrent attacks of multi-system inflammation caused by genetic mutations that result in abnormal upregulation of key innate immune mediators. The term autoinflammatory syndromes includes a broad variety of disorders, including cryopyrin-associated periodic syndromes (CAPS) such as neonatal onset multisystem inflammatory disease (NOMID), familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), periodic fever syndromes, including familial Mediterranean fever (FMF), TNF receptor-1 associated periodic syndrome (TRAPS), and Blau syndrome. Ocular manifestations are frequent and diverse in affected patients, and visual impairment and blindness are not uncommon sequelae of chronic active disease. Novel therapeutic interventions targeting specific pathophysiologic mechanisms have been extremely promising in the treatment of these disorders. The purpose of this article is to provide a review of these disorders with a focus on pathogenesis, clinical manifestations, ophthalmologic involvement, and available treatment options.

Blau syndrome, clinical and genetic aspects

Blau syndrome (BS) is a rare autosomal dominant, autoinflammatory syndrome characterized by the clinical triad of granulomatous recurrent uveitis, dermatitis and symmetric arthritis. The gene responsible for BS has been identified in the caspase recruitment domain gene CARD15/NOD2. In the majority of patients, the disease is characterized by early onset, usually before 3-4years of age. The manifestations at disease onset are usually represented by articular and cutaneous involvement signs, generally followed later by ocular manifestations which are often the most relevant morbidity of BS. In some cases the presence of fever is also observed; atypical cases of BS have been reported with cardiovascular, neurological, renal, intestinal and other organ involvement. The rarity and the variations in the severity and evolution of its expressions do not permit sufficient data about optimal treatment for patients with BS. The first step of therapy is represented by the use of corticosteroids and successively, in case of unsatisfactory response, by additional treatment with immunosuppressive agents. The results with biologic anti-cytokine agents, such as anti-TNFα and anti-IL1β, are different, particularly with regard to ocular morbidity. Clinical and genetic aspects of the familial and the sporadic form of BS will be discussed and focused on. A description of a case study of an Italian family is also included.

Blau Arteritis Resembling Takayasu Disease with a Novel NOD2 Mutation

Objective.

To put forward a new concept — Blau arteritis, a form of large-vessel vasculitis phenotypically related to Takayasu disease but genetically and clinically part of an expanded phenotype of Blau syndrome.

Methods.

We provide a clinical description of a new case and summarize previously published cases of arteritis associated with Blau syndrome. Genetic testing was performed by direct sequencing of exon 4 of the NOD2 gene.

Results.

The case described and those reviewed from the literature demonstrate the emerging phenotype of Takayasu-like arteritis in patients with Blau syndrome. Although most patients described to date depict an otherwise classic Blau syndrome phenotype, the current case was atypical in that the predominant features were arteritic. A novel substitution, G464W, in a highly conserved position near the nucleotide oligomerization domain of the NOD2 protein is also described.

Conclusion.

Blau arteritis can be observed in the context of both typical and atypical (incomplete) Blau syndrome. The associated mutation in the NOD2 gene raises the question of the potential importance of this gene among patients with “primary” forms of Takayasu arteritis.

Miscellaneous non-inflammatory musculoskeletal conditions. Blau syndrome

Blau syndrome (BS) is a rare dominantly inherited, inflammatory syndrome characterised by the clinical triad of granulomatous dermatitis, symmetric arthritis and recurrent uveitis. The caspase recruitment domain gene CARD15/NOD2 has been identified as the gene responsible for BS. In the majority of patients, the disease is characterised by early onset, usually before 3-4 years of age. Onset is most often articular and cutaneous. Eye symptoms usually start later; however, eye involvement is the most relevant morbidity of BS. Atypical cases of BS have been reported with involvement of organs other than skin, joint and eyes. Due to its rarity and the variations in the severity and evolution of its expressions, there have been no studies on the optimal treatment for patients with BS. If the therapeutic response to corticosteroids is unsatisfactory, additional treatment with immunosuppressive agents should be tried. The results with biologic anti-cytokine agents, such as infliximab and anakinra, are variable, particularly with regard to ocular morbidity. This review will focus on the clinical and genetics aspects of the familial and the sporadic form of BS. Further, we will describe an Italian family followed by us over the past 25 years.

The NLRP3 inflammasome is active but not essential in endotoxin-induced uveitis

OBJECTIVE

The inflammasome complex involving caspase-1 and nucleotide-binding domain, leucine-rich repeat containing protein (NLRP)3, also known as NALP3 or cryopyrin is important for host responses to microbial pathogens and several autoinflammatory diseases. We investigated the extent to which NLRP3 and caspase-1 control ocular interleukin (IL)-1β production and severity of uveitis (intraocular inflammatory disease) in an established, acute inflammatory uveitis model, endotoxin-induced uveitis (EIU).

METHODS

Expression of NLRP3, its adaptor molecule ASC, also known as PYCARD (PYD and CARD domain containing), and caspase-1 were examined by immunoblotting. IL-1β production was measured by enzyme-linked immunosorbent assay (ELISA). Using knockout mice, roles for caspase-1 and NLRP3 were examined in uveitis induced by intraocular injection of Escherichia coli lipopolysaccharide (LPS).

RESULTS

NLRP3, ASC, and caspase-1 proteins are constitutively expressed in eye tissue. During EIU, IL-1β protein production increases; this requires the presence of both caspase-1 and NLRP3. However, severity of EIU is not altered by deficiency in either caspase-1 or NLRP3, as assessed by both intravital microscopy and histology.

CONCLUSIONS

These data identify the importance of the NLRP3 inflammasome for IL-1β production in the eye, yet indicate that its participation in EIU is nonessential.

Interplay between innate and adaptive immunity in the development of non-infectious uveitis

In vertebrates, the innate and adaptive immune systems have evolved seamlessly to protect the host by rapidly responding to danger signals, eliminating pathogens and creating immunological memory as well as immunological tolerance to self. The innate immune system harnesses receptors that recognize conserved pathogen patterns and alongside the more specific recognition systems and memory of adaptive immunity, their interplay is evidenced by respective roles during generation and regulation of immune responses. The hallmark of adaptive immunity which requires engagement of innate immunity is an ability to discriminate between self and non-self (and eventually between pathogen and symbiont) as well as peripheral control mechanisms maintaining immunological health and appropriate responses. Loss of control mechanisms and/or regulation of either the adaptive or the innate immune system lead to autoimmunity and autoinflammation respectively. Although autoimmune pathways have been largely studied to date in the context of development of non-infectious intraocular inflammation, the recruitment and activation of innate immunity is required for full expression of the varied phenotypes of non-infectious uveitis. Since autoimmunity and autoinflammation implicate different molecular pathways, even though some convergence occurs, increasing our understanding of their respective roles in the development of uveitis will highlight treatment targets and influence our understanding of immune mechanisms operative in other retinal diseases. Herein, we extrapolate from the basic mechanisms of activation and control of innate and adaptive immunity to how autoinflammatory and autoimmune pathways contribute to disease development in non-infectious uveitis patients.

The CD40-CD40L axis and IFN-γ play critical roles in Langhans giant cell formation

The presence of Langhans giant cells (LGCs) is one of the signatures of systemic granulomatous disorders such as tuberculosis and sarcoidosis. However, the pathophysiological mechanism leading to LGC formation, especially the contribution of the T cells abundantly found in granulomas, has not been fully elucidated. To examine the role of T cells in LGC formation, a new in vitro method for the induction of LGCs was developed by co-culturing human monocytes with autologous T cells in the presence of concanavalin A (ConA). This system required close contact between monocytes and T cells, and CD4+ T cells were more potent than CD8+ T cells in inducing LGC formation. Antibody inhibition revealed that a CD40-CD40 ligand (CD40L) interaction and IFN-γ were essential for LGC formation, and the combination of exogenous soluble CD40L (sCD40L) and IFN-γ efficiently replaced the role of T cells. Dendritic cell-specific transmembrane protein (DC-STAMP), a known fusion-related molecule in monocytes, was up-regulated during LGC formation. Moreover, knock-down of DC-STAMP by siRNA inhibited LGC formation, revealing that DC-STAMP was directly involved in LGC formation. Taken together, these results demonstrate that T cells played a pivotal role in a new in vitro LGC formation system, in which DC-STAMP was involved, and occurred via a molecular mechanism that involved CD40-CD40L interaction and IFN-γ secretion.

NLRs in immune privileged sites

Innate immune receptors such as the nucleotide-binding domain, leucine-rich repeat-containing (NBD-LRR) receptors, referred to as NLRs, are known to serve as a critical component of host defense. However, their participation in inflammatory responses within immune privileged sites such as the brain and eye is less understood. The potential importance of NLRs in regulation of inflammation within these particular sites is further underscored by their association with autoinflammatory disorders, wherein localized inflammation can occur within the brain or eye as neuroinflammation or uveitis, respectively. Many NLRs are expressed within the brain and eye and in this review, we discuss their roles in the inflammation of the central nervous system (CNS) and uveitis.

[Hereditary systemic autoinflammatory diseases]

Systemic autoinflammatory diseases encompass different rare clinical entities characterized by recurrent acute inflammatory episodes secondary to a dysregulated inflammatory process. Since their first clinical descriptions, the Mendelian hereditary nature of some of them became evident, with their genetic and molecular basis being recently elucidated. There are disease-causing mutations in genes encoding for different proteins involved in the innate immune response and inflammation. Herein, we will introduce the reader to an updated review of the main clinical, physiopathological and therapeutic features of the different hereditary systemic autoinflammatory diseases.

Clinical immunology review series: An approach to the patient with a periodic fever syndrome

The periodic fever syndromes are disorders of innate immunity. They may be inherited or acquired and present as recurrent attacks of apparently spontaneous self-limiting inflammation without evidence of autoantibodies or infection. Over the past decade-and-a-half there has been significant progress in their understanding and treatment.

Uveitis in Blau syndrome from a de novo mutation of the NOD2/CARD15 gene

Blau syndrome (MIM 186580) is a rare autoinflammatory, familial granulomatous condition that occurs secondary to a single amino acid mutation of the NOD2/CARD15 gene on chromosome 16p12-q21. We report the case of a 2.5-year-old girl who presented for ophthalmic examination in the setting of rash and synovitis. Initially, small, evanescent, ovoid corneal subepithelial opacities unique to Blau syndrome were observed. She later developed a fulminant panuveitis that responded to immunomodulatory therapy. Subsequent genetic testing confirmed the diagnosis of Blau syndrome. Despite immunosuppression, at almost 7 years of age, she continues to have persistent panuveitis with vision of 20/20.

Autoinflammation: translating mechanism to therapy

Autoinflammatory syndromes are a clinically heterogeneous collection of diseases characterized by dysregulation of the innate immune system. The hereditary recurrent fever disorders were the first to be defined as autoinflammatory. Several of the responsible genes are now known to encode proteins forming multimeric complexes called inflammasomes, which are intracellular "danger sensors" that respond to a variety of different signals by activating caspase-1, responsible for cleavage and subsequent release of bioactive IL-1β. This discovery of the causative link between autoinflammation and IL-1β maturation has led to a significantly improved understanding of the mechanisms of innate immunity, as well as life-altering treatments for patients. Targeting IL-1β for the treatment of autoinflammatory syndromes is an excellent example of the power of translational research. Given the central role of inflammation in many complex multigenic diseases, these treatments may benefit larger numbers of patients in the future. Here, we review current treatment strategies of autoinflammatory diseases with a focus on IL-1 antagonism.

Treatment of autoinflammatory syndromes

PURPOSE OF REVIEW

Inherited autoinflammatory diseases are experiments in nature in which mutations of proteins playing a pivotal role in the regulation of the innate immunity lead to unprovoked episodes of inflammation. The understanding of the molecular pathways involved in these disorders has shed a new light on the pattern of activation and maintenance of the inflammatory response and disclosed new molecular therapeutic targets. In this review, we outline the more recent novelties in the treatment of autoinflammatory diseases and their possible implications for some multifactorial pediatric conditions.

RECENT FINDINGS

Cryopyrin-associated periodic syndrome (CAPS) represents the prototype of autoinflammatory diseases. The study of the pathophysiological consequence of mutations of the cryopyrin gene (NLRP3) allowed the identification of the intracellular pathways thought to play a pivotal part in the activation and secretion of the potent inflammatory cytokine interleukin (IL)-1β. The dramatic effect of IL-1 blockade in CAPS opens new perspectives for the treatment of other inherited and multifactorial inflammatory disorders. A number of IL-1 blockers are now available on the market.

SUMMARY

Studies on the pathogenesis and treatment of inherited autoinflammatory diseases are also changing the approach to some multifactorial inflammatory conditions.

Monogenic autoinflammatory diseases: new insights into clinical aspects and pathogenesis

PURPOSE OF REVIEW

The genetic and clinical characterizations of monogenic autoinflammatory syndromes have led to ground breaking insights into the regulation of inflammatory responses to endogenous and exogenous inducers or triggers of inflammation and continue to uncover key inflammatory pathways of the innate immune system. This article summarizes recent progress in the clinical aspects and understanding of the pathogenesis of this growing spectrum of diseases.

RECENT FINDINGS

The understanding of the spectrum of organ manifestations in autoinflammation was expanded by the discovery of two novel monogenic diseases both caused by the absence of an anti-inflammatory signal and added evidence that increased IL-1 signaling can cause aseptic osteolytic bone lesions and that the absence of IL-10 signaling causes inflammatory enterocolitis in neonates. New knock in animal models for TNF-receptor-associated periodic syndrome, and familial Mediterranean fever and cryopyrin-associated periodic syndromes allow insights into the complexity of the dysregulated immune pathways. Exploring 'triggers' of the NLRP3 inflammasome spurred studies of tissue inflammation in diseases including gout and those that previously have not been considered inflammatory in nature such as diabetes, fibrosing lung disease and possibly coronary artery disease.

SUMMARY

The genetic characterization of a growing number of monogenic autoinflammatory diseases has provided important insights into the phenotypic expression of single gene disorders and the complexity of the dysregulated inflammatory pathways leading to clinical disease. Knowledge obtained from these disorders is pertinent to a number of common disorders and provides new targets for drug development.

Blocking interleukin-1 in rheumatic diseases

The role of the potent proinflammatory cytokine IL-1 in disease could clinically be investigated with the development of the IL-1 blocking agent anakinra (Kineret), a recombinant IL-1 receptor antagonist. It was first tested in patients with sepsis without much benefit but was later FDA approved for the treatment of patients with rheumatoid arthritis. More recently IL-1 blocking therapies are used successfully to treat a new group of immune-mediated inflammatory conditions, autoinflammatory diseases. These conditions include rare hereditary fever syndromes and pediatric and adult conditions of Still's disease. Recently the FDA approved two additional longer acting IL-1 blocking agents, for the treatment of cryopyrin-associated periodic syndromes (CAPS), an IL-1 dependent autoinflammatory syndrome. The study of autoinflammatory diseases revealed mechanisms of IL-1 mediated organ damage and provided concepts to a better understanding of the pathogenesis of more common diseases such as gout and Type 2 diabetes which show initial promising results with IL-1 blocking therapy.

Therapy of autoinflammatory syndromes

The therapy of autoinflammatory syndromes is an excellent example of the power of translational research. Recent advances in our understanding of the molecular and immunologic basis of this newly identified classification of disease have allowed for the application of novel, effective, targeted treatments with life-changing effects on patients. Although colchicine and TNF-alpha inhibitors are important therapies for specific autoinflammatory syndromes, the novel IL-1-targeted drugs are particularly effective for many of these diseases. Recently, the pharmaceutical industry has adopted a strategy of confirming the efficacy of new targeted drugs in often-ignored patients with orphan diseases, and US Food and Drug Administration policies have allowed for accelerated approval of these drugs, creating a win-win situation for patients and industry. This article reviews the general approach to the therapy of autoinflammatory diseases, focusing on current approved therapies and novel approaches that might be used in the future.

Autoinflammation: the prominent role of IL-1 in monogenic autoinflammatory diseases and implications for common illnesses

The discovery of the genetic causes of a rare group of immune-mediated inflammatory conditions that mimic infections and allergic conditions in their clinical presentation and the molecular understanding of the function of the mutated molecules in these diseases has led to a revolution in our understanding of the pathogenesis of systemic and local inflammation. The proteins mutated in a number of these so-called autoinflammatory diseases are part of, or regulate the activity of, intracellular molecular complexes, the inflammasomes, that sense "danger" to the body and coordinate an initial immune response. Our understanding of specific triggers of the inflammasomes, coupled with the recognition that inflammasomes are critical for activation of the proinflammatory cytokine IL-1, has provided a rational and very effective target in the treatment of a number of these rare autoinflammatory diseases. In addition, the ongoing discovery of the role of inflammasomes and IL-1 activation and secretion in a number of genetically complex disorders have fundamentally changed our view of disease pathogenesis in a growing number of disorders that were heretofore not even thought of as "immunologic" diseases.

Sporadic Blau syndrome with onset of widespread granulomatous dermatitis in the newborn period

Blau syndrome is a dominantly inherited, chronic autoinflammatory disorder characterized by the clinical triad of granulomatous dermatitis, symmetric arthritis, and recurrent uveitis with onset below 4 years of age. It is caused by activating mutations in the nucleotide-binding oligomerization domain 2 (NOD2) gene, previously referred to as CARD15 gene. Noncaseating granulomas in affected tissues are the pathologic hallmark of the condition. We report the lifelong severe disease course in a 14-year-old Caucasian boy with sporadic Blau syndrome. Unusually, granulomatous dermatitis started in the first week of life. Whereas skin involvement faded away spontaneously in subsequent years, polyarthritis and anterior uveitis appeared in the second and third year of life respectively. Mutational analysis of the NOD2 gene revealed a missense mutation (R334W) previously detected in other Blau syndrome pedigrees. With this report, we would like to stress the rare possibility of Blau syndrome in generalized papular rashes of infancy and the importance of histopathologic study for clarification. The finding of early-onset widespread granulomatous dermatitis should prompt eye and joint examination in regular intervals and entail mutational analysis of the NOD2 gene.

Non-infectious pediatric uveitis: an update on immunomodulatory management

Pediatric non-infectious uveitis remains a rare but potentially sight-threatening group of diseases. However, early screening and treatment can improve outcomes. No single agent has proven to be efficacious in all cases. A wide variety of long-term immunomodulatory treatments are available; these agents differ in both their potency and side effect profiles. Corticosteroids remain an extremely valuable form of treatment in the short-term management of uveitis. Other major groups of immunomodulatory treatments include the calcineurin inhibitors and antimetabolites such as methotrexate, which is frequently used as the first-line agent. The biologics, including anti-tumor necrosis factor agents and interferons, are newer and potentially very useful therapies although side effects limit their use. Successful outcomes may be achieved with appropriate immunosuppressant therapy given early in the disease, although clinical trials are required to define the true efficacy of this strategy.

NOD2-associated pediatric granulomatous arthritis, an expanding phenotype: study of an international registry and a national cohort in Spain

OBJECTIVE

To study the phenotype characteristics of the largest to date cohort of patients with pediatric granulomatous arthritis (PGA) and documented mutations in the NOD2 gene.

METHODS

We analyzed merged data from 2 prospective cohorts of PGA patients, the International PGA Registry and a Spanish cohort. A systematic review of the medical records of interest was performed to identify phenotype characteristics.

RESULTS

Forty-five patients with PGA (23 sporadic cases and 22 from familial pedigrees) and documented NOD2 mutations were identified and formed the basis of the study. Of these 45 patients, 18 had the R334W-encoding mutation, 18 had R334Q, 4 had E383K, 3 had R587C, 1 had C495Y, and 1 had W490L. The majority of patients manifested the typical triad of dermatitis, uveitis, and arthritis. In contrast, in 13 patients, the following "atypical" manifestations were noted: fever, sialadenitis, lymphadenopathy, erythema nodosum, leukocytoclastic vasculitis, transient neuropathy, granulomatous glomerular and interstitial nephritis, interstitial lung disease, arterial hypertension, hypertrophic cardiomyopathy, pericarditis, pulmonary embolism, hepatic granulomatous infiltration, splenic involvement, and chronic renal failure. In addition, 4 individuals who were asymptomatic carriers of a disease-causing mutation were documented.

CONCLUSION

NOD2-associated PGA can be a multisystem disorder with significant visceral involvement. Treating physicians should be aware of the systemic nature of this condition, since some of these manifestations may entail long-term morbidity.

[Diagnostics and therapy of AA amyloidosis]

AA amyloidosis can be the consequence of any chronic inflammatory disorder. It is most commonly associated with chronic inflammatory rheumatic, pulmonary or gastrointestinal diseases, familial Mediterranean fever or other rare periodic syndromes. AA amyloidosis often affects the kidneys, gastrointestinal tract and the heart. Effective therapy of the underlying disease can normalize the inflammatory reaction and can slow or inhibit the deterioration of organ function if the diagnosis is made at an early stage of the disease. In rheumatoid diseases and in some periodic syndromes the use of antibodies against TNFalpha or IL-1 beta might be helpful. Patients with familial Mediterranean fever should regularly take colchicine to prevent attacks and to reduce the risk for development or progression of AA amyloidosis. Eprodisate is currently being investigated for AA amyloidosis and renal involvement.

Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*)

The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.