Periodic fever, mild arthralgias, and reversible moderate and severe organ inflammation associated with the V198M mutation in the CIAS1 gene in three German patients - expanding phenotype of CIAS1 related autoinflammatory syndrome

The role of the NLRP3 inflammasome and pyroptosis in cardiovascular diseases

An intense, stereotyped inflammatory response occurs in response to ischaemic and non-ischaemic injury to the myocardium. The NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome is a finely regulated macromolecular protein complex that senses the injury and triggers and amplifies the inflammatory response by activation of caspase 1; cleavage of pro-inflammatory cytokines, such as pro-IL-1β and pro-IL-18, to their mature forms; and induction of inflammatory cell death (pyroptosis). Inhibitors of the NLRP3 inflammasome and blockers of IL-1β and IL-18 activity have been shown to reduce injury to the myocardium and pericardium, favour resolution of the inflammation and preserve cardiac function. In this Review, we discuss the components of the NLRP3 inflammasome and how it is formed and activated in various ischaemic and non-ischaemic cardiac pathologies (acute myocardial infarction, cardiac dysfunction and remodelling, atherothrombosis, myocarditis and pericarditis, cardiotoxicity and cardiac sarcoidosis). We also summarize current preclinical and clinical evidence from studies of agents that target the NLRP3 inflammasome and related cytokines.

Emerging Roles of Inflammasomes in Cardiovascular Diseases

Cardiovascular diseases are known as the leading cause of morbidity and mortality worldwide. As an innate immune signaling complex, inflammasomes can be activated by various cardiovascular risk factors and regulate the activation of caspase-1 and the production and secretion of proinflammatory cytokines such as IL-1β and IL-18. Accumulating evidence supports that inflammasomes play a pivotal role in the progression of atherosclerosis, myocardial infarction, and heart failure. The best-known inflammasomes are NLRP1, NLRP3, NLRC4, and AIM2 inflammasomes, among which NLRP3 inflammasome is the most widely studied in the immune response and disease development. This review focuses on the activation and regulation mechanism of inflammasomes, the role of inflammasomes in cardiovascular diseases, and the research progress of targeting NLRP3 inflammasome and IL-1β for related disease intervention.

The NLRP3 inflammasome in acute myocardial infarction

The heart is extremely sensitive to ischaemic injury. During an acute myocardial infarction (AMI) event, the injury is initially caused by reduced blood supply to the tissues, which is then further exacerbated by an intense and highly specific inflammatory response that occurs during reperfusion. Numerous studies have highlighted the central role of the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome in this process. The inflammasome, an integral part of the innate immune system, is a macromolecular protein complex that finely regulates the activation of caspase 1 and the production and secretion of powerful pro-inflammatory cytokines such as IL-1β and IL-18. In this Review, we summarize evidence supporting the therapeutic value of NLRP3 inflammasome-targeted strategies in experimental models, and the data supporting the role of the NLRP3 inflammasome in AMI and its consequences on adverse cardiac remodelling, cytokine-mediated systolic dysfunction, and heart failure.

Inflammasomes in the Pathophysiology of Kidney Diseases

BACKGROUND

The inflammasome is a complex of proteins in the cytoplasm that consists of three main components: a sensor protein (receptor), an adapter protein and caspase-1. Inflammasomes are the critical components of innate immunity and have been gradually recognized as a critical mediator in various autoimmune diseases; also, their role in chronic kidney disease and acute kidney injury has been gradually accepted.

SUMMARY

Inflammasomes triggered by infectious or sterile injuries transfer proinflammatory mediators into mature ones through innate danger-signaling platforms. Information on inflammasomes in kidney disease will help to uncover the underlying mechanisms of nephropathy and provide novel therapeutic targets in the future.

KEY MESSAGES

The inflammasomes can be activated by a series of exogenous and endogenous stimuli, including pathogen-and danger-associated molecular patterns released from or caused by damaged cells. The NACHT, LRR and PYD domain-containing protein 3 (NLRP3) in the kidney exerts its effect not only by the 'canonical' pathway of IL-1β and IL-18 secretion but also by 'noncanonical' pathways, such as tumor growth factor-β signaling, epithelial-mesenchymal transition and fibrosis. In both clinical and experimental data, the NLRP3 inflammasome was reported to be involved in the pathogenesis of chronic kidney disease and acute kidney injury. However, the underlying mechanisms are not fully understood. Therapies targeting the activation of the NLRP3 inflammasome or blocking its downstream effectors appear attractive for the pursuit of neuropathy treatments.

Analysis of the genetic basis of periodic fever with aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome

PFAPA syndrome is the most common autoinflammatory syndrome in children from Western countries. In spite of its strong familial clustering, its genetic basis and inheritance pattern are still unknown. We performed a comprehensive genetic study on 68 individuals from 14 families. Linkage analysis suggested a susceptibility locus on chromosome 8, but direct molecular sequencing did not support this initial statistical finding. Exome sequencing revealed the absence of any gene that was mutated in all patients. Exhaustive screening of genes involved in other autoinflammatory syndromes or encoding components of the human inflammasome showed no DNA variants that could be linked to PFAPA molecular pathology. Among these, the previously-reported missense mutation V198M in the NLRP3 gene was clearly shown not to co-segregate with PFAPA. Our results on this relatively large cohort indicate that PFAPA syndrome is unlikely to be a monogenic condition. Moreover, none of the several genes known to be involved in inflammation or in autoinflammatory disorders seem to be relevant, alone, to its etiology, suggesting that PFAPA results from oligogenic or complex inheritance of variants in multiple disease genes and/or non-genetic factors.

Phenotypic and genotypic characteristics of cryopyrin-associated periodic syndrome: a series of 136 patients from the Eurofever Registry

OBJECTIVE

To evaluate genetic, demographic and clinical features in patients with cryopyrin-associated periodic syndrome (CAPS) from the Eurofever Registry, with a focus on genotype-phenotype correlations and predictive disease severity markers.

METHODS

A web-based registry retrospectively collected data on patients with CAPS. Experts in the disease independently validated all cases. Patients carrying NLRP3 variants and germline-mutation-negative patients were included.

RESULTS

136 patients were analysed. The median age at disease onset was 9 months, and the median duration of follow-up was 15 years. Skin rash, musculoskeletal involvement and fever were the most prevalent features. Neurological involvement (including severe complications) was noted in 40% and 12% of the patients, respectively, with ophthalmological involvement in 71%, and neurosensory hearing loss in 42%. 133 patients carried a heterozygous, germline mutation, and 3 patients were mutation-negative (despite complete NLRP3 gene screening). Thirty-one different NLRP3 mutations were recorded; 7 accounted for 78% of the patients, whereas 24 rare variants were found in 27 cases. The latter were significantly associated with early disease onset, neurological complications (including severe complications) and severe musculoskeletal involvement. The T348M variant was associated with early disease onset, chronic course and hearing loss. Neurological involvement was less strongly associated with V198M, E311 K and A439 V alleles. Early onset was predictive of severe neurological complications and hearing loss.

CONCLUSIONS

Patients carrying rare NLRP3 variants are at risk of severe CAPS; onset before the age of 6 months is associated with more severe neurological involvement and hearing loss. These findings may have an impact on treatment decisions.

Cytokine profile in a cohort of healthy blood donors carrying polymorphisms in genes encoding the NLRP3 inflammasome

Background

The NLRP3 inflammasome has been recognized as one of the key components of the innate immunity by sensing a diversity of insults. Inflammasome activation results in the maturation of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18. Increased production of IL-1β is found in patients with gain-of-function polymorphisms in genes encoding the NLRP3 inflammasome. Since approximately 5% of the Swedish population are heterozygote carriers of these combined gene variants, their impact on inflammasome status and a relationship on disease development is therefore highly relevant to study. The present study investigates levels of inflammasome-produced cytokines as a measure of inflammasome activation in healthy individuals carrying Q705K polymorphism in the NLRP3 gene combined with C10X in the CARD8 gene.

Materials and Methods

Genotyping of 1006 healthy blood donors was performed for the polymorphisms Q705K in the NLRP3 and C10X in the CARD8 genes. IL-1β, IL-18, IL-33, as well as a number of other pro-inflammatory cytokines, were analyzed by Luminex or ELISA in plasma from individuals carrying the polymorphisms and in age and gender matched non-carrier controls.

Results & Discussion

The prevalence of the polymorphisms was in line with previous studies. Plasma levels of IL-1β and IL-33 were elevated among carriers of combined Q705K+C10X polymorphisms compared to controls, whereas no difference was found for IL-18 and the other cytokines measured. Moreover, carriers of C10X or Q705K perse had similar plasma levels of IL-1β as non-carriers. These data suggest that the combined polymorphisms create inflammasomes with increased basal activation state, which might provide a more favourable innate immune response. In spite of this, it could also represent the mechanisms by which the inflammatory loop is triggered into a long-term inflammatory phenotype.

Clinical characteristics in subjects with NLRP3 V198M diagnosed at a single UK center and a review of the literature

Introduction

Mutations in the NLRP3 gene are associated with the dominantly inherited cryopyrin-associated periodic syndrome (CAPS). The significance of the V198M variant is unclear; it has been reported in association with various CAPS phenotypes and as a variant of uncertain consequence. The aim of this study was to characterize the clinical phenotypes and treatments in individuals with V198M assessed in a single UK center.

Methods

DNA samples from 830 subjects with fever syndromes or a family history of CAPS were screened for mutations in the NLRP3 gene with polymerase chain reaction (PCR) and sequencing. A detailed medical history was available in all cases. Inflammatory disease activity was monitored monthly with measurements of serum amyloid A protein (SAA) and C-reactive protein (CRP) in symptomatic individuals.

Results

NLRP3 V198M was identified in 19 subjects. It was found in association with CAPS in five cases, in one patient with Schnitzler syndrome, in three patients who also had a nucleotide alteration in another fever gene, and in three other patients with evidence of an autoinflammatory phenotype. Seven asymptomatic individuals were detected during screening of family members.

Conclusions

The NLRP3 V198M variant shows variable expressivity and reduced penetrance. It may be associated with classical inherited or apparently sporadic CAPS and with atypical autoinflammatory disease of varying severity, intriguingly including Schnitzler syndrome. The factors that influence the pathogenic consequences of this variant remain unknown. However, the remarkable response to interleukin 1 (IL-1) blockade in all but one individual in our series confirms that their clinical features are indeed mediated by IL-1.

NLRP3 E311K mutation in a large family with Muckle-Wells syndrome--description of a heterogeneous phenotype and response to treatment

Introduction

Muckle-Wells syndrome (MWS) is an inherited autoinflammatory disease characterized by fever, rash, arthralgia, conjunctivitis, sensorineural deafness and potentially life-threatening amyloidosis. The NLRP3/CIAS1 E311K mutation caused a heterogeneous phenotype of MWS in a large family. This study analyzes the clinical spectrum, patterns of inflammatory parameters and reports on response to treatment.

Methods

A total of 42 patients and family members were screened for the presence of the NLRP3 mutation. Clinical symptoms were reviewed in all family members. Classical (erythrocyte sedimentation rate (ESR, C-reactive protein (CRP)) and novel MWS inflammatory markers (serum amyloid A (SAA), cytokines, cytokine receptor levels) were determined. Patients were treated with the IL-1 inhibitors Anakinra or Canakinumab.

Results

All 13 clinically affected patients were heterozygous carriers of the amino acid substitution p.Glu311Lys/E311K encoded by exon 3 of the NLRP3 gene, but none of the healthy family members. Disease manifestations varied widely. Except for one child, all carriers suffered from hearing loss and severe fatigue. TNF-α, IL-6, TNF-RI, and TNF-RII levels as well as SAA were elevated in three, two, one, six and ten patients, respectively. Both clinical and laboratory parameters responded quickly and sustainedly to treatment with Anakinra or Canakinumab.

Conclusion

The NLRP3 E311K mutation is associated with a heterogeneous clinical spectrum, which may expand the view on MWS presentation. The leading symptom was hearing loss. Pericarditis, a rare but severe clinical feature of MWS, was diagnosed in three patients. One patient had a severe course, which led to renal failure secondary to amyloidosis. IL-1 inhibition leads to rapid and sustained improvement of symptoms.

Canakinumab (ACZ885, a fully human IgG1 anti-IL-1β mAb) induces sustained remission in pediatric patients with cryopyrin-associated periodic syndrome (CAPS)

INTRODUCTION

Cryopyrin-associated periodic syndrome (CAPS) represents a spectrum of three auto-inflammatory syndromes, familial cold auto-inflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease/chronic infantile neurological cutaneous and articular syndrome (NOMID/CINCA) with etiology linked to mutations in the NLRP3 gene resulting in elevated interleukin-1β (IL-1β) release. CAPS is a rare hereditary auto-inflammatory disease, which may start early in childhood and requires a life-long treatment. Canakinumab, a fully human anti-IL-1β antibody, produces sustained selective inhibition of IL-1β. This study was conducted to assess the efficacy, safety, and pharmacokinetics of canakinumab in the treatment of pediatric CAPS patients.

METHODS

Seven pediatric patients (five children and two adolescents) with CAPS were enrolled in a phase II, open-label study of canakinumab in patients with CAPS. Canakinumab was administered at a dose of 2 mg/kg subcutaneously (s.c.) (for patients with body weight ≤ 40 kg) or 150 mg s.c. (for patients with body weight > 40 kg) with re-dosing upon each relapse. The primary efficacy variable was time to relapse following achievement of a complete response (defined as a global assessment of no or minimal disease activity and no or minimal rash and values for serum C-reactive protein (CRP) and/or serum amyloid A (SAA) within the normal range, < 10 mg/L).

RESULTS

All patients achieved a complete response within seven days after the first dose of canakinumab and responses were reinduced on retreatment following relapse. Improvements in symptoms were evident within 24 hours after the first dose, according to physician assessments. The estimated median time to relapse was 49 days (95% CI 29 to 68) in children who received a dose of 2 mg/kg. Canakinumab was well tolerated. One serious adverse event, vertigo, was reported, but resolved during treatment.

CONCLUSIONS

Canakinumab, 2 mg/kg or 150 mg s.c., induced rapid and sustained clinical and biochemical responses in pediatric patients with CAPS.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT00487708.

Cerebrospinal fluid neopterin and cryopyrin-associated periodic syndrome

Cryopyrin-associated periodic syndrome is a category of autoinflammatory disorders caused by mutations of the NLRP3 gene, with chronic infantile neurologic cutaneous and articular syndrome being the severest clinical phenotype. Various pterins have been reported as mediating immunologic functions in the central nervous system, but to date studies of pterin cerebrospinal fluid (CSF) values and cryopyrin-associated periodic syndrome have been lacking. A 2-year-old child was affected with a severe atypical form of cryopyrin-associated periodic syndrome, suspected based on the analysis of neopterin in CSF. He initially presented isolated neurologic manifestations mimicking a neuroregressive disorder. Blood and CSF analyses did not present any routine inflammatory markers, but CSF neopterin was elevated. Later, the patient developed arthritis and recurrent episodes of fever, and the cryopyrin-associated periodic syndrome diagnosis was confirmed by genetic studies. Neopterin was the most altered indicator over the time. Child neurologists should be on the alert when unexplained neurologic signs appear, giving consideration to the possibility of inflammatory or immune-mediated diseases. The present case demonstrates the clinical utility of measurement of CSF neopterin levels in screening for these immune-mediated diseases, especially when neurologic symptoms are associated with normal results on routine CSF tests.

Familial cold auto-inflammatory syndrome (FCAS): characterization of symptomatology and impact on patients' lives

OBJECTIVE

Familial cold auto-inflammatory syndrome (FCAS), a subtype of cryopyrin-associated periodic syndromes (CAPS), is a rare, inherited disease that is virtually unknown to healthcare professionals. The aim of this patient survey was to characterize the symptomatology and evaluate the debilitating effects of FCAS on patients' daily lives.

RESEARCH DESIGN AND METHODS

Patients included in a disease database consisting of 167 FCAS and Muckle-Wells syndrome (MWS) patients were provided an opportunity to voluntarily participate in a cross-sectional market-based survey. Upon assessment of eligibility, individual in-depth phone interviews were conducted by an independent research agency to characterize disease symptomatology, diagnosis, and disease impact on daily activities.

RESULTS

Thirty patients with prior diagnosis of FCAS participated. The most common and recurring symptoms reported were rash, joint pain, chills, and fever. The majority of survey participants (90%) reported that they presented with symptoms as newborns or in early childhood - symptoms which became burdensome by school age, with patients reporting recurring symptoms and debilitating disease flares precipitated by environmental exposure to cooling temperatures. To cope with their underlying disease and to try to avoid symptomatic flares, patients reported limiting their work, school, family, and social activities. Seventy-eight percent of survey participants described an impact of the disease on their work, including absenteeism and impaired job advancement; frequently they quit their job as a consequence of their disease. Over 95% of survey participants reported that FCAS prevented participation in outdoor activities, while 83% indicated an impact on social activities, including relationships with friends and family. Limitations of this survey include the absence of a validated quality-of-life instrument, lack of correlation with patient medical records, and potential recall and responder bias. The number of participants appears small, but reflects 18% of the known FCAS population in the USA.

CONCLUSIONS

FCAS causes lifelong debilitating effects that restrict patients' daily lives. Poor recognition of this rare disease among healthcare professionals leads to delayed diagnosis and inappropriate or ineffective treatment. Healthcare providers need to be made aware of this serious debilitating disease to enable accurate and timely diagnosis and more compassionate management of this lifelong condition.

Periodic fever syndromes: a diagnostic challenge for the allergist

The objective was to present a case of periodic fever with aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA), summarize the medical literature on PFAPA, review the differential diagnosis and suggest a diagnostic approach to periodic fevers in children. A PubMed search was conducted for all case reports and series of patients with PFAPA. The references of these papers yielded further case reports. Review articles or large case series were used for sources of information regarding the other periodic fever and autoinflammatory syndromes. All cases reported as PFAPA were included in the review, even though a few of the cases may not have been accurately diagnosed. The periodic fever and autoinflammatory syndromes of childhood are a group of diseases that cause repeated febrile illnesses with various associated symptoms. Except for PFAPA, each of these diseases is caused by a known genetic mutation. Effective treatment options and long-term prognosis varies among these syndromes. Children with periodic fever or autoinflammatory syndromes sometimes present to an Allergy/Immunology clinic for immunologic evaluation. It is important for the Allergy/Immunology specialist to be familiar with the clinical presentation, diagnostic approach and treatment of these conditions.

Auto-inflammatory fever syndromes

Human autoinflammatory diseases (except for PFAPA) are a heterogeneous group of genetically determined diseases characterized by seemingly unprovoked inflammation in the absence of autoimmune or infective causes (Table 2). The last decade has witnessed tremendous advances in the understanding of these disorders. These advances have allowed therapeutic interventions resulting in improvement in the short-term and long-term morbidity of all of these diseases. Future research into the molecular mechanisms underlying these inflammatory diseases should lead to a better understanding of inflammatory diseases in general and, it is hoped, to better and more targeted therapies.

The clinical continuum of cryopyrinopathies: novel CIAS1 mutations in North American patients and a new cryopyrin model

OBJECTIVE

The cryopyrinopathies are a group of rare autoinflammatory disorders that are caused by mutations in CIAS1, encoding the cryopyrin protein. However, cryopyrin mutations are found only in 50% of patients with clinically diagnosed cryopyrinopathies. This study was undertaken to investigate the structural effect of disease-causing mutations on cryopyrin, in order to gain better understanding of the impact of disease-associated mutations on protein function.

METHODS

We tested for CIAS1 mutations in 22 patients with neonatal-onset multisystem inflammatory disease/chronic infantile neurologic, cutaneous, articular syndrome, 12 with Muckle-Wells syndrome (MWS), 18 with familial cold-induced autoinflammatory syndrome (FCAS), and 3 probands with MWS/FCAS. In a subset of mutation-negative patients, we screened for mutations in proteins that are either homologous to cryopyrin or involved in the caspase 1/interleukin-1beta signaling pathway. CIAS1 and other candidate genes were sequenced, models of cryopyrin domains were constructed using structurally homologous proteins as templates, and disease-causing mutations were mapped.

RESULTS

Forty patients were mutation positive, and 7 novel mutations, V262A, C259W, L264F, V351L, F443L, F523C, and Y563N, were found in 9 patients. No mutations in any candidate genes were identified. Most mutations mapped to an inner surface of the hexameric ring in the cryopyrin model, consistent with the hypothesis that the mutations disrupt a closed form of cryopyrin, thus potentiating inflammasome assembly. Disease-causing mutations correlated with disease severity only for a subset of known mutations.

CONCLUSION

Our modeling provides insight into potential molecular mechanisms by which cryopyrin mutations can inappropriately activate an inflammatory response. A significant number of patients who are clinically diagnosed as having cryopyrinopathies do not have identifiable disease-associated mutations.

Nonclassic neurologic features in cryopyrin-associated periodic syndromes

Neurologic manifestations in early childhood occur in the cryopyrin-associated periodic syndromes, especially in the chronic infantile neurological, cutaneous, and articular syndrome (CINCA) and the Muckle-Wells syndrome. Cryopyrin-associated periodic syndromes are commonly linked to mutations in the cold-induced autoinflammatory syndrome gene CIAS1 (current symbol, NLRP3) on chromosome 1. We describe three children with atypical cryopyrin-associated periodic syndromes, neurologic symptoms, and a Q705K mutation. Cryopyrin-associated periodic syndrome screening should be considered for children with neurologic and other periodic symptoms with elevated inflammatory markers. This syndrome is treatable with anakinra.

Identification of novel regulators in T-cell differentiation of aplastic anemia patients

BACKGROUND

Aplastic anemia (AA) is a bone marrow failure syndrome mostly characterized by an immune-mediated destruction of marrow hematopoietic progenitor/stem cells. The resulting hypocellularity limits a detailed analysis of the cellular immune response. To overcome this technical problem we performed a microarray analysis of CD3+ T-cells derived from bone marrow aspirates and peripheral blood samples of newly diagnosed AA patients and healthy volunteers. Two AA patients were additionally analyzed after achieving a partial remission following immunosuppression. The regulation of selected candidate genes was confirmed by real-time RT-PCR.

RESULTS

Among more than 22,200 transcripts, 583 genes were differentially expressed in the bone marrow of AA patients compared to healthy controls. Dysregulated genes are involved in T-cell mediated cytotoxicity, immune response of Th1 differentiated T-cells, and major regulators of immune function. In hematological remission the expression levels of several candidate genes tend to normalize, such as immune regulators and genes involved in proinflammatory immune response.

CONCLUSION

Our study suggests a pivotal role of Th1/Tc1 differentiated T-cells in immune-mediated marrow destruction of AA patients. Most importantly, immune regulatory genes could be identified, which are likely involved in the recovery of hematopoiesis and may help to design new therapeutic strategies in bone marrow failure syndromes.

Familial Mediterranean fever and the other autoinflammatory syndromes: evaluation of the patient with recurrent fever

PURPOSE OF REVIEW

The aim of this article is to summarize recent clinical, genetic and pathophysiologic findings of familial Mediterranean fever and several of the other systemic autoinflammatory diseases, a recently recognized group of disorders characterized by seemingly unprovoked inflammation but lacking high-titer autoantibodies. Genetic and clinical tools are improving the ability of the clinician to better approach patients with periodic fever and inflammation.

RECENT FINDINGS

The spectrum of reported genetic mutations and susceptible ethnicities for the hereditary periodic fever subset of the autoinflammatory diseases has continued to expand. At the same time, the pathogeneses of many of these diseases are now understood to involve different aspects of a common pathway, largely affecting inflammatory cascades related to IL-1 or tumor necrosis factor-alpha. Three of these diseases which have been grouped as the cryopyrin-associated periodic syndromes result from defects in the same gene, and all three appear to respond well to anti-IL-1 therapy although controlled trials are still in progress. In addition, cytokine-based therapies are also now under investigation for hyperimmunoglobulinemia D with periodic fever syndrome and pyogenic sterile arthritis, pyoderma gangrenosum, and acne syndrome.

SUMMARY

The identification of the genes and proteins mutated in many of the autoinflammatory diseases has broadened our understanding of the regulation of inflammation and the immune system, and provided the basis for the use of targeted therapies in these syndromes. We propose an algorithm for the evaluation of a patient with periodic fever, taking into account the patient's age, ethnicity, symptoms and signs, and results from laboratory and genetic testing.

Familial autoinflammatory diseases: genetics, pathogenesis and treatment

PURPOSE OF REVIEW

The systemic autoinflammatory diseases are characterized by seemingly unprovoked inflammation, without major involvement of the adaptive immune system. This review focuses mainly on a subset of these illnesses, the hereditary recurrent fevers, which include familial Mediterranean fever, the tumor necrosis factor receptor-associated periodic syndrome, the hyperimmunoglobulinemia D with periodic fever syndrome, and cryopyrin-associated periodic syndromes. This review elucidates how recent advances have impacted diagnosis, pathogenesis, and treatment.

RECENT FINDINGS

More than 170 mutations have been identified in the four genes underlying the six hereditary recurrent fevers. Genetic testing has broadened the clinical and geographic boundaries of these illnesses, given rise to the concept of the cryopyrin-associated periodic syndromes as a disease spectrum, and permitted diagnosis of compound heterozygotes for mutations in two different hereditary recurrent fever genes. Genetics has also advanced our understanding of amyloidosis, a complication of the hereditary recurrent fevers, and suggested a possible role for common hereditary recurrent fever variants in other inflammatory conditions. Recent advances in molecular pathophysiology include the elucidation of the N-terminal PYRIN domain in protein-protein interactions, the description of the NALP3 (cryopyrin) inflammasome as a macromolecular complex for interleukin-1beta activation, and the identification of signaling defects other than defective receptor shedding in patients with tumor necrosis factor receptor-associated periodic syndrome. These molecular insights form the conceptual basis for targeted biologic therapies.

SUMMARY

Advances in molecular genetics extend our ability to recognize and treat patients with systemic autoinflammatory diseases and inform our understanding of the regulation of innate immunity in humans.

Periodic fever syndromes

Human autoinflammatory diseases (except for the periodic fever, adenopathy, pharyngitis, aphthae syndrom) are a heterogeneous group of genetically determined diseases characterized by seemingly unprovoked inflammation, in the absence of autoimmune or infective causes. Tremendous advances in the understanding of these disorders have been seen in the last decade. This article discusses hereditary autoinflammatory syndromes that are associated with recurrent fevers.