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Necrotizing vasculitis is a classic lesion of polyarteritis nodosa (PAN) and a number of other disorders. This Perspectives article discusses how the characterization and understanding of PAN and related disorders has developed and enabled more-specific treatments. Polyarteritis nodosa (PAN) is a vasculitic disease characterized primarily by necrotizing vasculitis — inflammatory lesions in blood vessels that lead to vessel wall necrosis. Our understanding of PAN and necrotizing vasculitis has evolved over time. In addition to PAN, necrotizing vasculitis is now a recognized feature of a broad range of diseases with different aetiopathogenesis. For example, necrotizing vasculitis associated with hepatitis B virus infection has a different aetiopathogeneis to PAN and is now classified as a separate disease. Additionally, although 'classic' PAN is not an inherited disease, mutations in specific genes, such as ADA2 (also known as CECR1 ), can result in a necrotizing vasculopathy similar to PAN. The literature also suggests that the course of PAN differs in childhood-onset disease and in cases confined to the skin (so-called cutaneous PAN). Dissecting PAN and other autoinflammatory diseases with PAN-like features has enabled more-specific therapies and might also help us better understand the pathogenesis of these devastating conditions.

Key Points Monogenic autoinflammatory diseases can be classified on the basis of their dominating clinical feature (for example, periodic fever) or their pathogenesis (for example, as IL-1 or NFκB activation disorders) Among the monogenic autoinflammatory diseases, clinical diagnostic criteria have already been suggested for familial Mediterranean fever (FMF), and we suggest a flowchart to guide requests for mutation analysis of the associated gene FMF is an autosomal recessive disease; however, a single mutation, or a clear disease-causing mutation together with a variant with low penetrance, can be associated with the clinical phenotype Clinical classification criteria and flowcharts to guide physicians in decision-making and asking for specific genetic testing are also needed for other autoinflammatory diseases Anti-IL-1 treatment has shown promising results in many of the autoinflammatory diseases Autoinflammatory diseases are associated with abnormal activation of the innate immune system and resultant inflammation. Here, the authors provide a clinical and practical guide to autoinflammatory diseases, describing classification, insights into pathogenesis, diagnosis and management of these conditions. 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.

Familial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease (AID) affecting mainly the ethnic groups originating from Mediterranean basin. The disease is characterized by self-limited inflammatory attacks of fever and polyserositis along with elevated acute phase reactants. FMF is inherited autosomal recessively; however, a significant proportion of heterozygotes also express the phenotype. FMF is caused by mutations in the gene coding for pyrin, which is a component of inflammasome functioning in inflammatory response and production of interleukin-1β (IL-1β). Recent studies have shown that pyrin recognizes bacterial modifications in Rho GTPases, which results in inflammasome activation and increase in IL-1β. Pyrin does not directly recognize Rho modification but probably affected by Rho effector kinase, which is a downstream event in the actin cytoskeleton pathway. Recently, an international group of experts has published the recommendations for the management of FMF. Colchicine is the mainstay of FMF treatment, and its regular use prevents attacks and controls subclinical inflammation in the majority of patients. Furthermore, it decreases the long-term risk of amyloidosis. However, a minority of FMF patients fail to response or tolerate colchicine treatment. Anti-interleukin-1 drugs could be considered in these patients. One should keep in mind the possibility of non-compliance in colchicine-non-responders. Although FMF is a relatively well-described AID and almost 20 years has passed since the discovery of the gene, there are still a number of unsolved problems about it such as the exact mechanism of the disease, symptomatic heterozygotes and their treatment, and the optimal management of colchicine resistance.

Our aim was to report our experiences of pediatric macrophage activation syndrome (MAS) patients treated with anakinra and to review previous studies reporting anakinra treatment in pediatric MAS patients associated with systemic juvenile idiopathic arthritis (sJIA) or autoinflammatory diseases (AIDs). The study group consisted of pediatric MAS patients due to sJIA or AIDs, followed up in the Pediatric Rheumatology Unit of Hacettepe University between January 2015 and January 2017 and treated with anakinra (anti-IL1). We conducted a systematic review of the published literature involving pediatric MAS patients associated with sJIA or AIDs, treated with anakinra. Thirteen sJIA patients and two AIDs patients were included the study. Nineteen MAS episodes were observed in 15 patients. Anakinra (2 mg/kg/day) was started in with a median 1 day after admission. Clinical symptoms resolved, and laboratory findings normalized within median (minimum–maximum) 2 (1–4) and 6 (4–9) days, respectively after the introduction of anakinra. Steroid treatment was stopped in a median of 10 (4–13) weeks after the initiation of anakinra treatment. Patients were followed up for a median of 13 (6–24) months. Two patients developed recurrent MAS episodes when the anakinra dose was reduced, while the other patients achieved remission. In the literature review, we identified nine articles, describing 35 pediatric MAS patients associated with sJIA or AIDs and treated with anakinra. Except for two, all the patients reached remission. Our study and systematic literature review may help to improve the knowledge on the role of anakinra treatment in the management of MAS.

Chronic inflammatory arthritis in childhood is heterogeneous in presentation and course. Most forms exhibit clinical and genetic similarity to arthritis of adult onset, although at least one phenotype might be restricted to children. Nevertheless, paediatric and adult rheumatologists have historically addressed disease classification separately, yielding a juvenile idiopathic arthritis (JIA) nomenclature that exhibits no terminological overlap with adult-onset arthritis. Accumulating clinical, genetic and mechanistic data reveal the critical limitations of this strategy, necessitating a new approach to defining biological categories within JIA. In this Review, we provide an overview of the current evidence for biological subgroups of arthritis in children, delineate forms that seem contiguous with adult-onset arthritis, and consider integrative genetic and bioinformatic strategies to identify discrete entities within inflammatory arthritis across all ages.Childhood-onset arthritis has historically been treated as a separate entity to adult-onset arthritis, with its own nomenclature and classification system. Biological evidence has revealed the limitations of the current approach, necessitating a fresh look at the classification of paediatric arthritis.

Familial Mediterranean fever (FMF) is an autoinflammatory disease caused by homozygous or compound heterozygous gain-of-function mutations in MEFV , which encodes pyrin, an inflammasome protein. Heterozygous carrier frequencies for multiple MEFV mutations are high in several Mediterranean populations, suggesting that they confer selective advantage. Among 2,313 Turkish people, we found extended haplotype homozygosity flanking FMF-associated mutations, indicating evolutionarily recent positive selection of FMF-associated mutations. Two pathogenic pyrin variants independently arose >1,800 years ago. Mutant pyrin interacts less avidly with Yersinia pestis virulence factor YopM than with wild-type human pyrin, thereby attenuating YopM-induced interleukin (IL)-1β suppression. Relative to healthy controls, leukocytes from patients with FMF harboring homozygous or compound heterozygous mutations and from asymptomatic heterozygous carriers released heightened IL-1β specifically in response to Y.   pestis . Y.   pestis- infected Mefv M680I/M680I FMF knock-in mice exhibited IL-1-dependent increased survival relative to wild-type knock-in mice. Thus, FMF mutations that were positively selected in Mediterranean populations confer heightened resistance to Y.   pestis . Familial Mediterranean fever is an autoinflammatory disease caused by gain-of-function mutations in the pyrin inflammasome. Kastner and colleagues show that mutant pyrin better resists suppression by the plague bacterium Yersinia   pestis and may have been positively selected in human Middle Eastern populations.

Familial Mediterranean fever (FMF); is an autosomal recessively inherited autoinflammatory disease caused by the mutations in the Mediterranean Fever ( MEFV ) gene. Recent studies have shown that epigenetic control mechanisms, particularly non-coding RNAs, may play a role in the pathogenesis of autoinflammation. microRNAs (miRNAs) are small non-coding RNAs that play critical roles in regulating host gene expression at the post-transcriptional level. The phenotypic heterogeneity of FMF disease suggests that FMF may not be a monogenic disease, suggesting that epigenetic factors may affect phenotypic presentation. Here we examined the potential anti-inflammatory effect of miR-197-3p, which is a differentially expressed miRNA in FMF patients, by using inflammation related functional assays. We monitored gene expression levels of important cytokines, as well as performed functional studies on IL-1β secretion, caspase-1 activation, apoptosis assay, and cell migration assay. These experiments were used to evaluate the different stages of inflammation following pre-miR-197 transfection. Anti-miR-197 transfections were performed to test the opposite effect. 3′UTR luciferase activity assay was used for target gene studies. Our results obtained by inflammation-related functional assays demonstrated an anti-inflammatory effect of miR-197-3p in different cell types (synovial fibroblasts, monocytes, macrophages). 3′UTR luciferase activity assay showed that miR-197-3p directly binds to the interleukin-1beta (IL-1β) receptor, type I ( IL1R1 ) gene, which is one of the key molecules of the inflammatory pathways. This study may contribute to understand the role of miR-197-3p in autoinflammation process. Defining the critical miRNAs may guide the medical community in a more personalized medicine in autoinflammatory diseases.

Objective To present MRI distribution of active osteitis in a single tertiary referral center cohort of patients with chronic nonbacterial osteomyelitis (CNO). Methods Two musculoskeletal radiologists retrospectively reviewed MRI examinations of all patients with a final clinical diagnosis of CNO over 15 years. Sites of active osteitis at any time during the course of disease were divided into seven groups: (A) mandible, sternum, clavicles, or scapulas; (B) upper extremities; (C) subchondral sacrum and ilium immediately subjacent to sacroiliac joints (active osteitis denoting “active sacroiliitis” here); (D) pelvis and proximal 1/3 of femurs (excluding group C); (E) bones surrounding knees including distal 2/3 of femurs and 1/2 of proximal tibias and fibulas; (F) distal legs (including distal 1/2 of tibias and fibulas), ankles, or feet; (G) spine (excluding group C). Temporal changes of lesions in response to treatment (or other treatment-related changes such as pamidronate lines) were not within the scope of the study. Results Among 97 CNO patients (53 males [55%], 44 females; age at onset, mean ± SD, 8.5 ± 3.2 years; age at diagnosis, 10.3 ± 3.3 years), whole-body (WB) MRI was performed in 92%, mostly following an initial targeted MRI (94%). A total of 557 (346 targeted and 211 WB) MRIs were analyzed. Biopsy was obtained in 39 patients (40%), all consistent with CNO or featuring supporting findings. The most common locations for active osteitis were groups D (78%; 95% CI 69‒85%) and C (72%; 95% CI 62‒80%). Conclusion Pelvis and hips were preferentially involved in this cohort of CNO patients along with a marked presence of active sacroiliitis. Clinical relevance statement When suggestive findings of CNO are identified elsewhere in the body, the next targeted site of MRI should be the pelvis (entirely including sacroiliac joints) and hips, if whole-body MRI is not available or feasible. Key Points • Heavy reliance on MRI for diagnosis of CNO underscores the importance of suggestive distribution patterns. • Pelvis and hips are the most common (78%) sites of CNO involvement along with active sacroiliitis (72%). • Pelvis including sacroiliac joints and hips should be targeted on MRI when CNO is suspected.

BackgroundDifferent diagnostic and classification criteria are available for hereditary recurrent fevers (HRF)—familial Mediterranean fever (FMF), tumour necrosis factor receptor-associated periodic fever syndrome (TRAPS), mevalonate kinase deficiency (MKD) and cryopyrin-associated periodic syndromes (CAPS)—and for the non-hereditary, periodic fever, aphthosis, pharyngitis and adenitis (PFAPA). We aimed to develop and validate new evidence-based classification criteria for HRF/PFAPA.MethodsStep 1: selection of clinical, laboratory and genetic candidate variables; step 2: classification of 360 random patients from the Eurofever Registry by a panel of 25 clinicians and 8 geneticists blinded to patients’ diagnosis (consensus ≥80%); step 3: statistical analysis for the selection of the best candidate classification criteria; step 4: nominal group technique consensus conference with 33 panellists for the discussion and selection of the final classification criteria; step 5: cross-sectional validation of the novel criteria.ResultsThe panellists achieved consensus to classify 281 of 360 (78%) patients (32 CAPS, 36 FMF, 56 MKD, 37 PFAPA, 39 TRAPS, 81 undefined recurrent fever). Consensus was reached for two sets of criteria for each HRF, one including genetic and clinical variables, the other with clinical variables only, plus new criteria for PFAPA. The four HRF criteria demonstrated sensitivity of 0.94–1 and specificity of 0.95–1; for PFAPA, criteria sensitivity and specificity were 0.97 and 0.93, respectively. Validation of these criteria in an independent data set of 1018 patients shows a high accuracy (from 0.81 to 0.98).ConclusionEurofever proposes a novel set of validated classification criteria for HRF and PFAPA with high sensitivity and specificity.

Protein coding genes constitute only approximately 1% of the human genome but harbor 85% of the mutations with large effects on disease-related traits. Therefore, efficient strategies for selectively sequencing complete coding regions (i.e., \"whole exome\") have the potential to contribute to the understanding of rare and common human diseases. Here we report a method for whole-exome sequencing coupling Roche/NimbleGen whole exome arrays to the Illumina DNA sequencing platform. We demonstrate the ability to capture approximately 95% of the targeted coding sequences with high sensitivity and specificity for detection of homozygous and heterozygous variants. We illustrate the utility of this approach by making an unanticipated genetic diagnosis of congenital chloride diarrhea in a patient referred with a suspected diagnosis of Bartter syndrome, a renal salt-wasting disease. The molecular diagnosis was based on the finding of a homozygous missense D652N mutation at a position in SLC26A3 (the known congenital chloride diarrhea locus) that is virtually completely conserved in orthologues and paralogues from invertebrates to humans, and clinical follow-up confirmed the diagnosis. To our knowledge, whole-exome (or genome) sequencing has not previously been used to make a genetic diagnosis. Five additional patients suspected to have Bartter syndrome but who did not have mutations in known genes for this disease had homozygous deleterious mutations in SLC26A3. These results demonstrate the clinical utility of whole-exome sequencing and have implications for disease gene discovery and clinical diagnosis.