Multiple sclerosis in a patient with cryopyrin-associated autoinflammatory syndrome: Evidence that autoinflammation is the common link.

The co-existence of an autoinflammatory syndrome with a demyelinating disorder is a very rare occurrence raising the question whether there is a pathophysiological connection between them. We describe the case of a man with symptoms of cryopyrin-associated periodic syndrome (CAPS) since infancy who later developed multiple sclerosis (MS). As CAPS was genetically confirmed, the inhibition of interleukin-1 (IL-1) with anakinra led to a swift resolution of the CAPS symptoms and also, in combination with teriflunomide, to a clinical and imaging improvement of MS. In vitro studies showed that, upon a CAPS flare, the patient's peripheral neutrophils released neutrophil extracellular traps (NETs) decorated with IL-1ß, while NET release was markedly decreased following anakinra-induced remission of CAPS. Taking into account the growing evidence on the involvement of IL-1ß in experimental models of MS, this rare patient case suggests that the role of neutrophils/NETs and IL-1ß in MS should be further studied.

Novel Majeed Syndrome-Causing LPIN2 Mutations Link Bone Inflammation to Inflammatory M2 Macrophages and Accelerated Osteoclastogenesis.

OBJECTIVE: To identify novel heterozygous LPIN2 mutations in a patient with Majeed syndrome and characterize the pathomechanisms that lead to the development of sterile osteomyelitis. METHODS: Targeted genetic analysis and functional studies assessing monocyte responses, macrophage differentiation, and osteoclastogenesis were conducted to compare the pathogenesis of Majeed syndrome to interleukin-1 (IL-1)-mediated diseases including neonatal-onset multisystem inflammatory disease (NOMID) and deficiency of the IL-1 receptor antagonist (DIRA). RESULTS: A 4-year-old girl of mixed ethnic background presented with sterile osteomyelitis and elevated acute-phase reactants. She had a 17.8-kb deletion on the maternal LPIN2 allele and a splice site mutation, p.R517H, that variably spliced out exons 10 and 11 on the paternal LPIN2 allele. The patient achieved long-lasting remission receiving IL-1 blockade with canakinumab. Compared to controls, monocytes and monocyte-derived M1-like macrophages from the patient with Majeed syndrome and those with NOMID or DIRA had elevated caspase 1 activity and IL-1ß secretion. In contrast, lipopolysaccharide-stimulated, monocyte-derived, M2-like macrophages from the patient with Majeed syndrome released higher levels of osteoclastogenic mediators (IL-8, IL-6, tumor necrosis factor, CCL2, macrophage inflammatory protein 1α/ß, CXCL8, and CXCL1) compared to NOMID patients and healthy controls. Accelerated osteoclastogenesis in the patient with Majeed syndrome was associated with higher NFATc1 levels, enhanced JNK/MAPK, and reduced Src kinase activation, and partially responded to JNK inhibition and IL-1 (but not IL-6) blockade. CONCLUSION: We report 2 novel compound heterozygous disease-causing mutations in LPIN2 in an American patient with Majeed syndrome. LPIN2 deficiency drives differentiation of proinflammatory M2-like macrophages and enhances intrinsic osteoclastogenesis. This provides a model for the pathogenesis of sterile osteomyelitis which differentiates Majeed syndrome from other IL-1-mediated autoinflammatory diseases.

Induced pluripotent stem cell-derived monocytic cell lines from a NOMID patient serve as a screening platform for modulating NLRP3 inflammasome activity.

Curative therapeutic options for a number of immunological disorders remain to be established, and approaches for identifying drug candidates are relatively limited. Furthermore, phenotypic screening methods using induced pluripotent stem cell (iPSC)-derived immune cells or hematopoietic cells need improvement. In the present study, using immortalized monocytic cell lines derived from iPSCs, we developed a high-throughput screening (HTS) system to detect compounds that inhibit IL-1ß secretion and NLRP3 inflammasome activation from activated macrophages. The iPSCs were generated from a patient with neonatal onset multisystem inflammatory disease (NOMID) as a model of a constitutively activated NLRP3 inflammasome. HTS of 4,825 compounds including FDA-approved drugs and compounds with known bioactivity identified 7 compounds as predominantly IL-1ß inhibitors. Since these compounds are known inflammasome inhibitors or derivatives of, these results prove the validity of our HTS system, which can be a versatile platform for identifying drug candidates for immunological disorders associated with monocytic lineage cells.

ß-Glucan-induced reprogramming of human macrophages inhibits NLRP3 inflammasome activation in cryopyrinopathies.

Exposure of mononuclear phagocytes to ß-glucan, a naturally occurring polysaccharide, contributes to the induction of innate immune memory, which is associated with long-term epigenetic, metabolic, and functional reprogramming. Although previous studies have shown that innate immune memory induced by ß-glucan confers protection against secondary infections, its impact on autoinflammatory diseases, associated with inflammasome activation and IL-1ß secretion, remains poorly understood. In particular, whether ß-glucan-induced long-term reprogramming affects inflammasome activation in human macrophages in the context of these diseases has not been explored. We found that NLRP3 inflammasome-mediated caspase-1 activation and subsequent IL-1ß production were reduced in ß-glucan-reprogrammed macrophages. ß-Glucan acted upstream of the NLRP3 inflammasome by preventing potassium (K+) efflux, mitochondrial ROS (mtROS) generation, and, ultimately, apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization and speck formation. Importantly, ß-glucan-induced memory in macrophages resulted in a remarkable attenuation of IL-1ß secretion and caspase-1 activation in patients with an NLRP3-associated autoinflammatory disease, cryopyrin-associated periodic syndromes (CAPS). Our findings demonstrate that ß-glucan-induced innate immune memory represses IL-1ß-mediated inflammation and support its potential clinical use in NLRP3-driven diseases.

A novel knock-in mouse model of cryopyrin-associated periodic syndromes with development of amyloidosis: Therapeutic efficacy of proton pump inhibitors.

BACKGROUND: Cryopyrin-associated periodic syndromes (CAPS) are a group of autoinflammatory diseases linked to gain-of-function mutations in the NOD-like receptor family, pyrin domain containing 3 (NLRP3) gene, which cause uncontrolled IL-1ß secretion. Proton pump inhibitors (PPIs), which are commonly used as inhibitors of gastric acid production, also have anti-inflammatory properties, protect mice from sepsis, and prevent IL-1ß secretion by monocytes from patients with CAPS. OBJECTIVE: We sought to develop a novel Nlrp3 knock-in (KI) mouse model of CAPS to study amyloidosis, a severe CAPS complication, and test novel therapeutic approaches. METHODS: We generated KI mice by engineering the N475K mutation, which is associated with the CAPS phenotype, into the mouse Nlrp3 gene. KI and wild-type mice received PPIs or PBS intraperitoneally and were analyzed for survival, inflammation, cytokine secretion, and amyloidosis development. RESULTS: Mutant Nlrp3 KI mice displayed features that recapitulate the immunologic and clinical phenotype of CAPS. They showed systemic inflammation with high levels of serum proinflammatory cytokines, inflammatory infiltrates in various organs, and amyloid deposits in the spleen, liver, and kidneys. Toll-like receptor stimulated macrophages from KI mice secreted high levels of IL-1ß, IL-18, and IL-1α but low amounts of IL-1 receptor antagonist. Treatment of KI mice with PPIs had a clear clinical effect, showing a reduction in inflammatory manifestations, regression of amyloid deposits, and normalization of proinflammatory and anti-inflammatory cytokine production by macrophages. CONCLUSION: Nlrp3 KI mice displayed a CAPS phenotype with many characteristics of autoinflammation, including amyloidosis. The therapeutic effectiveness of PPIs associated with a lack of toxicity indicates that these drugs could represent relevant adjuvants to the anti-IL-1 drugs in patients with CAPS and other IL-1-driven diseases.

Low-frequency mosaicism in cryopyrin-associated periodic fever syndrome: mosaicism in systemic autoinflammatory diseases.

Autoinflammatory disease is an 'inborn error of immunity', resulting in systemic inflammation. Cryopyrin-associated periodic syndrome (CAPS) is a prototypical autoinflammatory disease caused by gain-of-function mutations in the NLRP3 (NLR family pyrin domain containing 3) gene; these mutations activate the NLRP3 inflammasome, resulting in overproduction of IL-1ß. The first case of CAPS caused by somatic NLRP3 mosaicism was reported in 2005 after identification of variant small peaks by Sanger sequencing. An international collaborative study revealed that the majority of mutation-negative CAPS cases are due to low-level NLRP3 mosaicism, suggesting that central nervous system involvement in somatic mosaicism patients is milder than in genotype-matched heterozygous patients. Recent advances in next-generation sequencing have expanded the number of NLRP3 somatic mosaicism cases and identified a new entity called 'late-onset CAPS with myeloid-specific NLRP3 mosaicism'; however, no mosaic-specific clinical features have been identified/confirmed yet. With respect to NLRP3 mosaicism in CAPS, a prospective longitudinal study on the variant genotype, its allele frequency and its tissue distribution (along with a comprehensive clinical phenotype) would provide better understanding of NLRP3 mosaicism, resulting in more appropriate patient care and genetic counseling.

Rapid and Sustained Long-Term Efficacy and Safety of Canakinumab in Patients With Cryopyrin-Associated Periodic Syndrome Ages Five Years and Younger.

OBJECTIVE: To assess long-term efficacy and safety of canakinumab and the response to vaccination in children ages ≤5 years with cryopyrin-associated periodic syndrome (CAPS). METHODS: CAPS patients (ages ≤5 years) received 2 mg/kg canakinumab subcutaneously every 8 weeks; patients with neonatal-onset multisystem inflammatory disease (NOMID) received a starting dose of 4 mg/kg in this open-label trial. Efficacy was evaluated using physician global assessment of disease activity and serum levels of C-reactive protein (CRP) and amyloid A (SAA). Adverse events (AEs) were recorded. Vaccination response was evaluated using postvaccination antibody titers at 4 and 8 weeks after immunization. RESULTS: Of the 17 patients enrolled, 12 (71%) had Muckle-Wells syndrome, 4 (24%) had NOMID, and 1 (6%) had familial cold autoinflammatory syndrome. All 17 patients had a complete response to canakinumab. Disease activity improved according to the physician global assessment, and for 65% of the patients autoinflammatory disease was characterized as "absent" at the end of the study. Median CRP levels decreased over time. No such change was evident in SAA levels. During the extension study, postvaccination antibody titers increased above protective levels in 16 (94%) of 17 assessable vaccinations. Ten of the patients (59%) had AEs suspected to be related to canakinumab; 8 (47%) experienced at least 1 serious AE (SAE). None of the AEs or SAEs required interruption of canakinumab therapy. CONCLUSION: Our findings indicate that canakinumab effectively maintains efficacy through 152 weeks and appears to have no effect on the ability to produce antibodies against standard childhood non-live vaccines. The safety profile of canakinumab was consistent with previous studies, supporting long-term use of canakinumab for CAPS in children ≤5 years of age.

CAPS and NLRP3.

Cryopyrin-associated periodic syndrome (CAPS) is a rare inherited autoinflammatory disorder characterized by systemic, cutaneous, musculoskeletal, and central nervous system inflammation. Gain-of-function mutations in NLRP3 in CAPS patients lead to activation of the cryopyrin inflammasome, resulting in the inappropriate release of inflammatory cytokines including IL-1ß and CAPS-related inflammatory symptoms. Several mechanisms have been identified that are important for the normal regulation of the cryopyrin inflammasome in order to prevent uncontrolled inflammation. Investigators have taken advantage of some of these pathways to develop and apply novel targeted therapies, which have resulted in improved quality of life for patients with this orphan disease.

Unveiling the Efficacy, Safety, and Tolerability of Anti-Interleukin-1 Treatment in Monogenic and Multifactorial Autoinflammatory Diseases.

Autoinflammatory diseases (AIDs) are heterogeneous disorders characterized by dysregulation in the inflammasome, a large intracellular multiprotein platform, leading to overproduction of interleukin-1(IL-1)ß that plays a predominant pathogenic role in such diseases. Appropriate treatment is crucial, also considering that AIDs may persist into adulthood with negative consequences on patients' quality of life. IL-1ß blockade results in a sustained reduction of disease severity in most AIDs. A growing experience with the human IL-1 receptor antagonist, Anakinra (ANA), and the monoclonal anti IL-1ß antibody, Canakinumab (CANA), has also been engendered, highlighting their efficacy upon protean clinical manifestations of AIDs. Safety and tolerability have been confirmed by several clinical trials and observational studies on both large and small cohorts of AID patients. The same treatment has been proposed in refractory Kawasaki disease, an acute inflammatory vasculitis occurring in children before 5 years, which has been postulated to be autoinflammatory for its phenotypical and immunological similarity with systemic juvenile idiopathic arthritis. Nevertheless, minor concerns about IL-1 antagonists have been raised regarding their employment in children, and the development of novel pharmacological formulations is aimed at minimizing side effects that may affect adherence to treatment. The present review summarizes current findings on the efficacy, safety, and tolerability of ANA and CANA for treatment of AIDs and Kawasaki vasculitis with a specific focus on the pediatric setting.

Inflammasome-Dependent Cytokines at the Crossroads of Health and Autoinflammatory Disease.

As key regulators of both innate and adaptive immunity, it is unsurprising that the activity of interleukin (IL)-1 cytokine family members is tightly controlled by decoy receptors, antagonists, and a variety of other mechanisms. Additionally, inflammasome-mediated proteolytic maturation is a prominent and distinguishing feature of two important members of this cytokine family, IL-1ß and IL-18, because their full-length gene products are biologically inert. Although vital in antimicrobial host defense, deregulated inflammasome signaling is linked with a growing number of autoimmune and autoinflammatory diseases. Here, we focus on introducing the diverse inflammasome types and discussing their causal roles in periodic fever syndromes. Therapies targeting IL-1 or IL-18 show great efficacy in some of these autoinflammatory diseases, although further understanding of the molecular mechanisms leading to unregulated production of these key cytokines is required to benefit more patients.

Analysis of NLRP3, MVK and TNFRSF1A variants in adult Greek patients with autoinflammatory symptoms.

OBJECTIVES: Autoinflammatory diseases are characterised by abnormal hyperactivity of the innate immune system, causing systemic inflammation. The cryopyrin associated periodic syndrome (CAPS), the hyper IgD syndrome (HIDS) and the TNF receptor-associated periodic syndrome (TRAPS), are autoinflammatory conditions associated with mutations in the NLRP3, MVK and TNFRSF1A genes, respectively. We present the experience of our Department with these rare syndromes analysing genetic and clinical data of adult patients encountered between January 2011 and September 2017. METHODS: Eighty-eight adult patients with clinical suspicion of CAPS, HIDS and TRAPS were sequentially recruited and genetically tested for specific mutations in NLRP3, MVK and TNFRSF1A using Sanger sequencing. Clinical picture of mutation carriers was reviewed. Allele frequencies were compared to those described for the normal population by the 1000 Genomes project. RESULTS: Seventy-two of the 88 adult patients were found to be positive for mutations or polymorphisms. One patient carried two pathogenic MVK mutations (pV377I/c.1129G>A and c.850delG) and another one carried a pathogenic heterozygous pΑ439V/c.1316C>T NLRP3 mutation. Seventeen patients carried variants of uncertain significance. The pS434S/c.1302C>T NLRP3 mutation is slightly increased in our patients compared to the reference population and seems to correlate with severe symptom presentation. CONCLUSIONS: In rare cases, periodic fever and inflammatory symptoms in adults can be attributed to mutations in NLRP3, MVK and TNFRSF1A. Clinical assessment and genetic analysis are critical for proper diagnosis and treatment of autoinflammatory diseases.

Complement receptor CD46 co-stimulates optimal human CD8+ T cell effector function via fatty acid metabolism.

The induction of human CD4+ Th1 cells requires autocrine stimulation of the complement receptor CD46 in direct crosstalk with a CD4+ T cell-intrinsic NLRP3 inflammasome. However, it is unclear whether human cytotoxic CD8+ T cell (CTL) responses also rely on an intrinsic complement-inflammasome axis. Here we show, using CTLs from patients with CD46 deficiency or with constitutively-active NLRP3, that CD46 delivers co-stimulatory signals for optimal CTL activity by augmenting nutrient-influx and fatty acid synthesis. Surprisingly, although CTLs express NLRP3, a canonical NLRP3 inflammasome is not required for normal human CTL activity, as CTLs from patients with hyperactive NLRP3 activity function normally. These findings establish autocrine complement and CD46 activity as integral components of normal human CTL biology, and, since CD46 is only present in humans, emphasize the divergent roles of innate immune sensors between mice and men.

Development and effect of antibodies to anakinra during treatment of severe CAPS: sub-analysis of a long-term safety and efficacy study.

Anakinra is an effective, well-tolerated, long-term anti-inflammatory treatment for cryopyrin-associated periodic syndromes (CAPS), yet evidence shows that it can induce the development of anti-drug antibodies (ADA). This analysis aims to determine ADA occurrence in CAPS patients and elucidate their effects on anakinra dosing and drug efficacy. A post hoc analysis was performed on data from a long-term safety and efficacy study in patients with severe CAPS. Patients were initiated on an anakinra dose of 1.0-2.4 mg/kg once daily subcutaneously, which was increased (in 0.5-1.0 mg/kg increments) to 2.0-5.0 mg/kg/day according to clinical need (median 3.1 mg/kg/day). ADA, serum amyloid A (SAA), and C-reactive protein (CRP) levels were measured at various time points, and pharmacokinetic (PK) parameters at 1 and 3 months. Efficacy was evaluated using a diary symptom sum score (DSSS), and SAA and CRP levels were evaluated as proxies of efficacy. Safety was evaluated by an analysis of adverse events (AEs). Anakinra dose levels were unrelated to ADA status. A high proportion of patients with at least one post-baseline assessment developed ADA (83%), the majority (79%) within 3 months. However, anakinra treatment markedly improved symptoms and was effective regardless of the presence of ADA; the annual rates of AEs were comparable between ADA-negative and ADA-positive patients. While ADA are likely to occur in CAPS patients treated with anakinra, our evidence shows that chronic daily subcutaneous treatment with anakinra is safe and effective regardless of the development and presence of ADA.

A dermatologic perspective on autoinflammatory diseases.

Autoinflammatory diseases (AIDs) encompass a heterogeneous group of disorders pathogenetically related to an abnormal activation of the innate immunity and clinically characterised by aseptic inflammation in the affected organs in the absence of high titer of circulating autoantibodies or autoreactive T cells. In classic monogenic AIDs, the skin is frequently involved with a wide range of cutaneous lesions. Monogenic AIDs result from different mutations in a single gene, which regulates the innate immunity. These mutations cause an uncontrolled activation of the inflammasome, leading to an overexpression of interleukin (IL)- 1ß. IL-1ß is the pivotal cytokine which is responsible for the exaggerated production of cytokines and chemokines that induce the recruitment of neutrophils, key cells in autoinflammation. Paradigmatic autoinflammatory forms are the cryopyrin-associated periodic syndromes (CAPS), whose skin involvement consists of urticarial lesions. Similar IL-1ß-mediated autoinflammatory pathomechanisms also occur in deficiency of IL-1 receptor antagonist (DIRA) and deficiency of IL-36 receptor antagonist (DITRA), whose cutaneous appearance is characterised by pustular lesions, as well as in pyogenic arthritis, pyoderma gangrenosum and acne (PAPA) syndrome. Pyoderma gangrenosum, which is the cutaneous hallmark of the PAPA syndrome, is a prototypic neutrophil-mediated skin disease, manifesting as single or multiple ulcers with undermined, raised erythematous to violaceous borders. This review is focused on the CAPS, DIRA/DITRA and PAPA syndromes with emphasis on their cutaneous manifestations, as well as their histology and pathophysiology.

Gain of function mutation and inflammasome driven diseases in human and mouse models.

Activation of the NLRP3 inflammasome, a multiprotein complex, leading to caspase activation with production of proinflammatory IL-1ß represents a major pathway of inflammation. Recent, studies in mice and human patients uncovered several gain-of- function (GOF) mutations in inflammasome sensor proteins that allow inflammasome assembly in the absence of cognate ligands to trigger autoinflammatory syndromes. Cryopyrin-associated periodic syndromes (CAPS) are rare autoinflammatory diseases, comprising a broad disease spectrum with varying severity. CAPS are associated with GOF mutations in the NLRP3 inflammasome and activation of IL-1ß leading to episodes of fever, cutaneous, musculoskeletal, articular, ocular, and neurological symptoms. Here, we review current knowledge on different mutations leading to CAPS and related clinical syndromes. Homologous gene mutations in mice provide insights into the regulation and consequences of the activation of different inflammasomes in several autoinflammatory syndrome. In view of the critical role of IL-1ß in the pathogenesis of autoinflammatory GOF mutations such as CAPS, blockade of the action of IL-1ß is critical. Therapeutic administration of recombinant IL-1 receptor antagonists or monoclonal anti-IL-1ß antibody had a beneficial effect. Furthermore, novel inhibitors of inflammasome complex formation such as MCC950 and related compounds attenuate experimental and clinical disease. The discovery of new GOF mutants of inflammasomes leading to further insights in pathomechanisms and the development of novel inhibitors represent a great challenge.

Multigene sequencing reveals heterogeneity of NLRP12-related autoinflammatory disorders.

NLRP12-related autoinflammatory disease (NLRP12-AID) is an exceptionally rare autosomal dominant disorder caused by germline mutations in NLRP12 gene. Very few patients with NLRP12-AD have been identified worldwide; therefore, there is a scarcity of data on phenotypic presentation of this syndrome. Here we provide evidence that NLRP12-AID may have clinical manifestations characteristic for primary immune deficiencies (PID). 246 children with periodic fever (PF) of unknown origin were subjects to the next generation sequencing (NGS) analysis; 213 of these patients had signs of primary immunodeficiency (PID) manifested by recurrent infections, while 33 kids had isolated PF. The NGS panel was composed of 302 genes implicated in PID and/or AID. 15 patients (9 girls and 6 boys) with NLRP12-AID were identified. Median age of first AID-related fever episode was 12 months, ranging from 2 months to 13 years. Main clinical features of NLRP12-related AID were periodic fever (100%), abdominal pain and diarrhea (47%), arthralgia (20%), headache (20%) and failure to thrive (33%). Nine patients demonstrated increased susceptibility to infection and two children suffered from Crohn's disease. Administration of short courses of NSAID or corticosteroids resulted in resolution of the disease flare. In one severe case, canakinumab (anti-interleukin-1ß antibody) was successfully used. Significant number of patients with genetically assigned diagnosis of NLPR12-AID has clinical features which close resemble primary immune deficiency. This phenotypic overlap may result in underdiagnosis of NLPR12-AID among patients with PID.

Repositioning Drugs for Rare Immune Diseases: Hopes and Challenges for a Precision Medicine.

Human primary immunodeficiency diseases (PIDs) are a large group of rare diseases and are characterized by a great genetic and phenotypic heterogeneity. A large subset of PIDs is genetically defined, which has a crucial impact for the understanding of the molecular basis of disease and the development of precision medicine. Discovery and development of new therapies for rare diseases has long been de-privileged due to the length and cost of the processes involved. Interest has increased due to stimulatory regulatory and supportive reimbursement environments enabling viable business models. Advancements in biomedical and computational sciences enable the development of rational, designed approaches for identification of novel indications of already approved drugs allowing faster delivery of new medicines. Drug repositioning is based either on clinical analogies of diseases or on understanding of the molecular mode of drug action and mechanisms of the disease. All of these are the basis for the development of precision medicine.

Remodelling of the gut microbiota by hyperactive NLRP3 induces regulatory T cells to maintain homeostasis.

Inflammasomes are involved in gut homeostasis and inflammatory pathologies, but the role of NLRP3 inflammasome in these processes is not well understood. Cryopyrin-associated periodic syndrome (CAPS) patients with NLRP3 mutations have autoinflammation in skin, joints, and eyes, but not in the intestine. Here we show that the intestines of CAPS model mice carrying an Nlrp3 R258W mutation maintain homeostasis in the gut. Additionally, such mice are strongly resistant to experimental colitis and colorectal cancer; this is mainly through a remodelled gut microbiota with enhanced anti-inflammatory capacity due to increased induction of regulatory T cells (Tregs). Mechanistically, NLRP3R258W functions exclusively in the lamina propria mononuclear phagocytes to directly enhance IL-1ß but not IL-18 secretion. Increased IL-1ß boosts local antimicrobial peptides to facilitate microbiota remodelling. Our data show that NLRP3R258W-induced remodelling of the gut microbiota, induces local Tregs to maintain homeostasis and compensate for otherwise-detrimental intestinal inflammation.

A high and equal prevalence of the Q703K variant in NLRP3 patients with autoinflammatory symptoms and ethnically matched controls.

OBJECTIVES: Cryopyrin associated periodic syndromes (CAPS) comprise a spectrum of autoinflammatory disorders of varying severity caused by mutations in the NLRP3 gene. The NLRP3-Q703K allele has been reported both as a functional polymorphism and as a low penetrance mutation. METHODS: To describe the clinical phenotype of subjects with the Q703K allele and to report the frequency of this allele among patients with autoinflammatory symptoms and healthy controls. To this end, a cohort of 10 ethnically-matched controls per each Q703K-carrying patient, was composed. RESULTS: Ninety patients suspected of harboring a systemic autoinflammatory disease (SAID), exclusive of FMF, were referred to our center for genotyping between 2012 and 2015. Fourteen of them (15.5%) were found to carry the Q703K allele, compared to 22 of 130 (16.9%) healthy, ethnically matched controls. CONCLUSIONS: The similar carrier rate of the NLRP3-Q703K allele among patients with manifestations of a SAID and an ethnically matched control group suggest that this variant, does not determine the clinical phenotype. This reiterates the importance of testing a control group to avoid erroneously attributing a causative role to a gene polymorphism.