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ISG15 deficiency is a rare disease caused by autosomal recessive variants in the ISG15 gene, which encodes the ISG15 protein. The ISG15 protein plays a dual role in both the type I and II interferon (IFN) immune pathways. Extracellularly, the ISG15 protein is essential for IFN-γ-dependent anti-mycobacterial immunity, while intracellularly, ISG15 is necessary for USP18-mediated downregulation of IFN-α/β signalling. Due to this dual role, ISG15 deficiency can present with various clinical phenotypes, ranging from susceptibility to mycobacterial infection to autoinflammation characterised by necrotising skin lesions, intracerebral calcification, and pulmonary involvement. In this report, we describe novel variants found in two different families that result in complete ISG15 deficiency and severe skin ulceration. Whole exome sequencing identified a heterozygous missense p.Q16X ISG15 variant and a heterozygous multigene 1p36.33 deletion in the proband from the first family. In the second family, a homozygous total ISG15 gene deletion was detected in two siblings. We also conducted further analysis, including characterisation of cytokine dysregulation, interferon-stimulated gene expression, and p-STAT1 activation in lymphocytes and lesional tissue. Finally, we demonstrate the complete and rapid resolution of clinical symptoms associated with ISG15 deficiency in one sibling from the second family following treatment with the Janus kinase (JAK) inhibitor baricitinib., Competing Interests: PB has received institutional grants from: Novartis, SOBI, Roche, Chemocentryx, and Novimmune; consultancy fees from Roche, Novartis and SOBI; and speaker fees from UCB. DE has received institutional grants from Lilly, Sobi, Roche and Pfizer. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Burleigh, Moraitis, Al Masroori, Al-Abadi, Hong, Omoyinmi, Titheradge, Stals, Jones, Gait, Jayarajan, Di, Sebire, Solman, Ogboli, Welch, Sudarsanam, Wacogne, Price-Kuehne, Jensen, Brogan and Eleftheriou.)

Objective: Several monogenic autoinflammatory disorders and primary immunodeficiencies can present early in life with features that may be mistaken for Behçet's disease (BD). We aimed to develop a genetic analysis workflow to identify rare monogenic BD-like diseases and establish the contribution of HLA haplotype in a cohort of patients from the UK., Methods: Patients with clinically suspected BD were recruited from four BD specialist care centres in the UK. All participants underwent whole exome sequencing (WES), and genetic analysis thereafter by 1. examining genes known to cause monogenic immunodeficiency, autoinflammation or vasculitis by virtual panel application; 2. scrutiny of variants prioritised by Exomiser using Human Phenotype Ontology (HPO); 3. identification of copy number variants using ExomeDepth; and 4. HLA-typing using OptiType., Results: Thirty-one patients were recruited: median age 15 (4-52), and median disease onset age 5 (0-20). Nine/31 (29%) patients had monogenic disease mimicking BD: 5 cases of Haploinsufficiency of A20 with novel TNFAIP3 variants (p.T76I, p.M112Tfs*8, p.S548Dfs*128, p.C657Vfs*14, p.E661Nfs*36); 1 case of ISG15 deficiency with a novel nonsense variant (ISG15:p.Q16X) and 1p36.33 microdeletion; 1 case of Common variable immune deficiency (TNFRSF13B:p.A181E); and 2 cases of TNF receptor associated periodic syndrome (TNFRSF1A:p.R92Q). Of the remaining 22 patients, 8 (36%) were HLA-B*51 positive., Conclusion: We describe a novel genetic workflow for BD, which can efficiently detect known and potentially novel monogenic forms of BD, whilst additionally providing HLA-typing. Our results highlight the importance of genetic testing before BD diagnosis, since this has impact on choice of therapy, prognosis, and genetic counselling., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Introduction: Accurate and standardized phenotypic descriptions are essential in diagnosing rare diseases and discovering new diseases, and the Human Phenotype Ontology (HPO) system was developed to provide a rich collection of hierarchical phenotypic descriptions. However, although the HPO terms for inborn errors of immunity have been improved and curated, it has not been investigated whether this curation improves the diagnosis of systemic autoinflammatory disease (SAID) patients. Here, we aimed to study if improved HPO annotation for SAIDs enhanced SAID identification and to demonstrate the potential of phenotype-driven genome diagnostics using curated HPO terms for SAIDs., Methods: We collected HPO terms from 98 genetically confirmed SAID patients across eight different European SAID expertise centers and used the LIRICAL (Likelihood Ratio Interpretation of Clinical Abnormalities) computational algorithm to estimate the effect of HPO curation on the prioritization of the correct SAID for each patient., Results: Our results show that the percentage of correct diagnoses increased from 66% to 86% and that the number of diagnoses with the highest ranking increased from 38 to 45. In a further pilot study, curation also improved HPO-based whole-exome sequencing (WES) analysis, diagnosing 10/12 patients before and 12/12 after curation. In addition, the average number of candidate diseases that needed to be interpreted decreased from 35 to 2., Discussion: This study demonstrates that curation of HPO terms can increase identification of the correct diagnosis, emphasizing the high potential of HPO-based genome diagnostics for SAIDs., Competing Interests: MH is currently employed by Boehringer Ingelheim RCV GmbH & Co KG. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Maassen, Legger, Kul Cinar, van Daele, Gattorno, Bader-Meunier, Wouters, Briggs, Johansson, van der Velde, Swertz, Omoyinmi, Hoppenreijs, Belot, Eleftheriou, Caorsi, Aeschlimann, Boursier, Brogan, Haimel and van Gijn.)

We describe a novel, severe autoinflammatory syndrome characterized by neuroinflammation, systemic autoinflammation, splenomegaly, and anemia (NASA) caused by bi-allelic mutations in IRAK4 . IRAK-4 is a serine/threonine kinase with a pivotal role in innate immune signaling from toll-like receptors and production of pro-inflammatory cytokines. In humans, bi-allelic mutations in IRAK4 result in IRAK-4 deficiency and increased susceptibility to pyogenic bacterial infections, but autoinflammation has never been described. We describe 5 affected patients from 2 unrelated families with compound heterozygous mutations in IRAK4 (c.C877T (p.Q293*)/c.G958T (p.D320Y); and c.A86C (p.Q29P)/c.161 + 1G>A) resulting in severe systemic autoinflammation, massive splenomegaly and severe transfusion dependent anemia and, in 3/5 cases, severe neuroinflammation and seizures. IRAK-4 protein expression was reduced in peripheral blood mononuclear cells (PBMC) in affected patients. Immunological analysis demonstrated elevated serum tumor necrosis factor (TNF), interleukin (IL) 1 beta (IL-1β), IL-6, IL-8, interferon α2a (IFN-α2a), and interferon β (IFN-β); and elevated cerebrospinal fluid (CSF) IL-6 without elevation of CSF IFN-α despite perturbed interferon gene signature. Mutations were located within the death domain (DD; p.Q29P and splice site mutation c.161 + 1G>A) and kinase domain (p.Q293*/p.D320Y) of IRAK-4. Structure-based modeling of the DD mutation p.Q29P showed alteration in the alignment of a loop within the DD with loss of contact distance and hydrogen bond interactions with IRAK-1/2 within the myddosome complex. The kinase domain mutation p.D320Y was predicted to stabilize interactions within the kinase active site. While precise mechanisms of autoinflammation in NASA remain uncertain, we speculate that loss of negative regulation of IRAK-4 and IRAK-1; dysregulation of myddosome assembly and disassembly; or kinase active site instability may drive dysregulated IL-6 and TNF production. Blockade of IL-6 resulted in immediate and complete amelioration of systemic autoinflammation and anemia in all 5 patients treated; however, neuroinflammation has, so far proven recalcitrant to IL-6 blockade and the janus kinase (JAK) inhibitor baricitinib, likely due to lack of central nervous system penetration of both drugs. We therefore highlight that bi-allelic mutation in IRAK4 may be associated with a severe and complex autoinflammatory and neuroinflammatory phenotype that we have called NASA (neuroinflammation, autoinflammation, splenomegaly and anemia), in addition to immunodeficiency in humans., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cooray, Price-Kuehne, Hong, Omoyinmi, Burleigh, Gilmour, Ahmad, Choi, Bahar, Torpiano, Gagunashvili, Jensen, Bellos, Sancho-Shimizu, Herberg, Mankad, Kumar, Kaliakatsos, Worth, Eleftheriou, Whittaker and Brogan.)

Neutrophilic inflammation is a hallmark of many monogenic autoinflammatory diseases; pathomechanisms that regulate extravasation of damaging immune cells into surrounding tissues are poorly understood. Here we identified three unrelated boys with perinatal-onset of neutrophilic cutaneous small vessel vasculitis and systemic inflammation. Two patients developed liver fibrosis in their first year of life. Next-generation sequencing identified two de novo truncating variants in the Src-family tyrosine kinase, LYN, p.Y508*, p.Q507* and a de novo missense variant, p.Y508F, that result in constitutive activation of Lyn kinase. Functional studies revealed increased expression of ICAM-1 on induced patient-derived endothelial cells (iECs) and of β2-integrins on patient neutrophils that increase neutrophil adhesion and vascular transendothelial migration (TEM). Treatment with TNF inhibition improved systemic inflammation; and liver fibrosis resolved on treatment with the Src kinase inhibitor dasatinib. Our findings reveal a critical role for Lyn kinase in modulating inflammatory signals, regulating microvascular permeability and neutrophil recruitment, and in promoting hepatic fibrosis., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

There is an important unmet clinical need for fast turnaround next generation sequencing (NGS) to aid genetic diagnosis of patients with acute and sometimes catastrophic inflammatory presentations. This is imperative for patients who require precise and targeted treatment to prevent irreparable organ damage or even death. Acute and severe hyper- inflammation may be caused by primary immunodeficiency (PID) with immune dysregulation, or more typical autoinflammatory diseases in the absence of obvious immunodeficiency. Infectious triggers may be present in either immunodeficiency or autoinflammation. We compiled a list of 25 genes causing monogenetic immunological diseases that are notorious for their acute first presentation with fulminant inflammation and which may be amenable to specific treatment, including hemophagocytic lymphohistiocytosis (HLH); and autoinflammatory diseases that can present with early-onset stroke or other irreversible neurological inflammatory complications. We designed and validated a pipeline that enabled return of clinically actionable results in hours rather than weeks: the Rapid Autoinflammation Panel (RAP). We demonstrated accuracy of this new pipeline, with 100% sensitivity and 100% specificity. Return of results to clinicians was achieved within 48-hours from receiving the patient's blood or saliva sample. This approach demonstrates the potential significant diagnostic impact of NGS in acute medicine to facilitate precision medicine and save "life or limb" in these critical situations., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 McCreary, Omoyinmi, Hong, Jensen, Burleigh, Price-Kuehne, Gilmour, Eleftheriou and Brogan.)

Background Idiopathic recurrent pericarditis (IRP) is an orphan disease that carries significant morbidity, partly driven by corticosteroid dependence. Innate immune modulators, colchicine and anti-interleukin-1 agents, pioneered in monogenic autoinflammatory diseases, have demonstrated remarkable efficacy in trials, suggesting that autoinflammation may contribute to IRP. This study characterizes the phenotype of patients with IRP and monogenic autoinflammatory diseases, and establishes whether autoinflammatory disease genes are associated with IRP. Methods and Results We retrospectively analyzed the medical records of patients with IRP (n=136) and monogenic autoinflammatory diseases (n=1910) attending a national center (London, UK) between 2000 and 2021. We examined 4 genes ( MEFV, MVK, NLRP3, TNFRSF1A ) by next-generation sequencing in 128 patients with IRP and compared the frequency of rare deleterious variants to controls obtained from the Genome Aggregation Database. In this cohort of patients with IRP, corticosteroid dependence was common (39/136, 28.7%) and was associated with chronic pain (adjusted odds ratio 2.8 [95% CI, 1.3-6.5], P =0.012). IRP frequently manifested with systemic inflammation (raised C-reactive protein [121/136, 89.0%] and extrapericardial effusions [68/136, 50.0%]). Pericarditis was observed in all examined monogenic autoinflammatory diseases (0.4%-3.7% of cases). Rare deleterious MEFV variants were more frequent in IRP than in ancestry-matched controls (allele frequency 9/200 versus 2932/129 200, P =0.040). Conclusions Pericarditis is a feature of interleukin-1 driven monogenic autoinflammatory diseases and IRP is associated with variants in MEFV , a gene involved in interleukin-1β processing. We also found that corticosteroid dependence in IRP is associated with chronic noninflammatory pain. Together these data implicate autoinflammation in IRP and support reducing reliance on corticosteroids in its management.

Deficiency of adenosine deaminase type 2 (DADA2) is an autosomal recessive disease caused by bi-allelic loss-of-function mutations in ADA2 . Treatment with anti-TNF is effective for the autoinflammatory and vasculitic components of the disease but does not correct marrow failure or immunodeficiency; and anti-drug antibodies cause loss of efficacy over time. Allogeneic haematopoietic stem cell transplantation may be curative, but graft versus host disease remains a significant concern. Autologous gene therapy would therefore be an attractive longer-term therapeutic option. We investigated whether lentiviral vector (LV)-mediated ADA2 gene correction could rescue the immunophenotype of DADA2 in primary immune cells derived from patients and in cell line models. Lentiviral transduction led to: i) restoration of ADA2 protein expression and enzymatic activity; (ii) amelioration of M1 macrophage cytokine production, IFN-γ and phosphorylated STAT1 expression in patient-derived macrophages; and (iii) amelioration of macrophage-mediated endothelial activation that drives the vasculitis of DADA2. We also successfully transduced human CD34+ haematopoietic stem progenitor cells (HSPC) derived from a DADA2 patient with pure red cell aplasia and observed restoration of ADA2 expression and enzymatic activity in CD34+HSPC, alongside recovery of stem-cell proliferative and colony forming unit capacity. These preclinical data now expand the evidence for the efficacy of gene transfer strategies in DADA2, and strongly support clinical translation of a lentivirus-mediated gene therapy approach to treat DADA2., Competing Interests: PB has received institutional grants from: Novartis, SOBI, Roche, Chemocentryx, and Novimmune; consultancy fees from Roche, Novartis and SOBI; and speaker fees from UCB. DE received institutional grants from Lilly, Sobi, Roche and Pfizer. All research at Great Ormond Street Hospital NHS Foundation Trust and UCL Great Ormond Street Institute of Child Health is made possible by the NIHR Great Ormond Street Hospital Biomedical Research Centre. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Hong, Casimir, Houghton, Zhang, Jensen, Omoyinmi, Torrance, Papadopoulou, Cummins, Roderick, Thrasher, Brogan and Eleftheriou.)

Background: Mevalonate kinase deficiency (MKD) is a rare autoinflammatory condition caused by biallelic loss-of-function (LOF) mutations in mevalonate kinase (MVK) gene encoding the enzyme mevalonate kinase. Patients with MKD display a variety of non-specific clinical manifestations, which can lead to diagnostic delay. We report the case of a child presenting with vasculitis that was found by genetic testing to be caused by MKD, and now add this autoinflammatory disease to the ever-expanding list of causes of monogenic vasculitides., Case Presentation: A 2-year-old male presented with an acute 7-day history of high-grade fever, abdominal pain, diarrhoea, rectal bleeding and extensive purpuric and necrotic lesions, predominantly affecting the lower limbs. He had been suffering from recurrent episodes of fever from early in infancy, associated with maculopapular/petechial rashes triggered by intercurrent infection, and after vaccines. Extensive infection screen was negative. Skin biopsy revealed small vessel vasculitis. Visceral digital subtraction arteriography was normal. With a diagnosis of severe idiopathic cutaneous vasculitis, he was treated with corticosteroids and mycophenolate mofetil. Despite that his acute phase reactants remained elevated, fever persisted and the vasculitic lesions progressed. Next-generation sequencing revealed compound heterozygous mutation in MVK c.928G > A (p.V310M) and c.1129G > A (p.V377I) while reduced mevalonate enzyme activity was confirmed suggesting a diagnosis of MKD as a cause of the severe vasculitis. Prompt targeted treatment with IL-1 blockade was initiated preventing escalation to more toxic vasculitis therapies and reducing unnecessary exposure to cytotoxic treatment., Conclusions: Our report highlights the broad clinical phenotype of MKD that includes severe cutaneous vasculitis and emphasizes the need to consider early genetic screening for young children presenting with vasculitis to exclude a monogenic vasculitis which may be amenable to targeted treatment., (© 2021. The Author(s).)

Background: Myhre syndrome is a genetic disorder caused by gain of function mutations in the SMAD Family Member 4 (SMAD4) gene, resulting in progressive, proliferative skin and organ fibrosis. Skin thickening and joint contractures are often the main presenting features of the disease and may be mistaken for juvenile scleroderma., Case Presentation: We report a case of a 13 year-old female presenting with widespread skin thickening and joint contractures from infancy. She was diagnosed with diffuse cutaneous systemic sclerosis, and treatment with corticosteroids and subcutaneous methotrexate recommended. There was however disease progression prompting genetic testing. This identified a rare heterozygous pathogenic variant c.1499 T > C (p.Ile500Thr) in the SMAD4 gene, suggesting a diagnosis of Myhre syndrome. Securing a molecular diagnosis in this case allowed the cessation of immunosuppression, thus reducing the burden of unnecessary and potentially harmful treatment, and allowing genetic counselling., Conclusion: Myhre Syndrome is a rare genetic mimic of scleroderma that should be considered alongside several other monogenic diseases presenting with pathological fibrosis from early in life. We highlight this case to provide an overview of these genetic mimics of scleroderma, and highlight the molecular pathways that can lead to pathological fibrosis. This may provide clues to the pathogenesis of sporadic juvenile scleroderma, and could suggest novel therapeutic targets.

Objective: To report a series of patients with cerebral arteriopathy associated with heterozygous variants in the casitas B-lineage lymphoma ( CBL ) gene and examine the functional role of the identified mutant Cbl protein. We hypothesized that mutated Cbl fails to act as a negative regulator of the RAS-mitogen-activated protein kinases (MAPK) signaling pathway, resulting in enhanced vascular fibroblast proliferation and migration and enhanced angiogenesis and collateral vessel formation., Methods: We performed whole-exome sequencing in 11 separate families referred to Great Ormond Street Hospital, London, with suspected genetic cause for clinical presentation with severe progressive cerebral arteriopathy., Results: We identified heterozygous variants in the CBL gene in 5 affected cases from 3 families. We show that impaired CBL -mediated degradation of cell surface tyrosine kinase receptors and dysregulated intracellular signaling through the RAS-MAPK pathway contribute to the pathogenesis of the observed arteriopathy. Mutated CBL failed to control the angiogenic signal relay of vascular endothelial growth factor receptor 2, leading to prolonged tyrosine kinase signaling, thus driving angiogenesis and collateral vessel formation. Mutant Cbl promoted myofibroblast migration and proliferation contributing to vascular occlusive disease; these effects were abrogated following treatment with a RAF-RAS-MAPK pathway inhibitor., Conclusions: We provide a possible mechanism for the arteriopathy associated with heterozygous CBL variants. Identification of the key role for the RAS-MAPK pathway in CBL -mediated cerebral arteriopathy could facilitate identification of novel or repurposed druggable targets for treating these patients and may also provide therapeutic clues for other cerebral arteriopathies., (Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objectives: Hereditary systemic autoinflammatory diseases are rare genetic disorders, which if untreated, can be complicated by AA amyloidosis leading to renal failure and premature death. Our objective was to find a genetic cause in a British family with a dominantly inherited autoinflammatory disease complicated by AA amyloidosis., Methods: The index patient and his sister underwent comprehensive clinical and laboratory assessment including the next-generation sequencing panel targeting autoinflammatory genes. Subsequently, other relatives underwent clinical evaluation and genetic testing. Screening of the SAA1 gene was performed in all symptomatic cases., Results: The index case and his sister presented with proteinuria due to AA amyloidosis. They have been suffering from episodes of fever accompanied by severe abdominal and chest pain, arthritis and erythema since childhood. Their father died aged 52 years from complications following a cadaveric renal transplantation. The post-mortem examination demonstrated AA amyloidosis. The index case's grandmother, two paternal cousins and two of their children described similar symptoms. All symptomatic individuals had excellent responses to colchicine. Next-generation sequencing analysis identified a single MEFV p.P373L variant in the index case, his sister and subsequently, in symptomatic family members. Sequencing of the SAA1 gene revealed all cases were heterozygous for the SAA1.1 allele., Conclusion: Typically FMF is an autosomal recessive disorder; nonetheless rare cases of dominantly inherited disease have previously been described. Here we report a novel MEFV variant p.P373L, causing dominant FMF complicated by AA amyloidosis in four generations of a British family., (© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

We identified a consanguineous kindred, of three affected children with severe autoinflammation, resulting in the death of one sibling and allogeneic stem cell transplantation in the other two. All three were homozygous for MEFV p.S208C mutation; however, their phenotype was more severe than previously reported, prompting consideration of an oligogenic autoinflammation model. Further genetic studies revealed homozygous mutations in TRAP1 , encoding the mitochondrial/ER resident chaperone protein tumour necrosis factor receptor associated protein 1 (TRAP1). Identification of a fourth, unrelated patient with autoinflammation and compound heterozygous mutation of TRAP1 alone facilitated further functional studies, confirming the importance of this protein as a chaperone of misfolded proteins with loss of function, which may contribute to autoinflammation. Impaired TRAP1 function leads to cellular stress and elevated levels of serum IL-18. This study emphasizes the importance of considering digenic or oligogenic models of disease in particularly severe phenotypes and suggests that autoinflammatory disease might be enhanced by bi-allelic mutations in TRAP1 ., (© 2019 Standing et al.)

Monogenic forms of vasculitis are rare but increasingly recognized. Furthermore, genetic immunodeficiency is increasingly associated with inflammatory immune dysregulatory features, including vasculitis. This case report describes a child of non-consanguineous parents who presented with chronic digital vasculitis early in life, is of short stature, has facial dysmorphia, immunodeficiency (low serum IgA, high serum IgM), recurrent bacterial infections, lymphoproliferation, absence of detectable serum C1q, and low classical complement pathway activity. We identified a previously reported de novo heterozygous pathogenic splice mutation in PIK3R1 (c.1425 + 1G > A), resulting in the skipping of exon 11 of the p85α subunit of phosphatidylinositol 3-kinase and causing activated PI3Kδ syndrome type II (APDS2). This explained the phenotype, with the exception of digital vasculitis and C1q deficiency, which have never been described in association with APDS2. No mutations were identified in C1QA, B , or C , their promoter regions, or in any other complement component. Functional studies indicated normal monocytic C1q production and release, suggesting that the observed C1q deficiency was caused by peripheral consumption of C1q. Since C1q deficiency has never been associated with APDS2, we assessed C1q levels in two unrelated patients with genetically confirmed APDS2 and confirmed C1q deficiency in those two cases as well. This observation suggests C1q deficiency to be an inherent but previously unrecognized feature of APDS2. We speculate that the consumption of C1q is driven by increased apoptotic bodies derived from immune cellular senescence, combined with elevated IgM production (both inherent features of APDS2). Secondary C1q deficiency in APDS2 may further contribute to immunodeficiency and could also be associated with inflammatory immune dysregulatory phenotypes, such as the digital vasculitis observed in our case., (Copyright © 2019 Hong, Nanthapisal, Omoyinmi, Olbrich, Neth, Speckmann, Lucena, Gilmour, Worth, The Genomics England Research Consortium, Klein, Eleftheriou and Brogan.)

Importance: Neuroinflammatory disorders are a range of severe neurological disorders causing brain and spinal inflammation and are now increasingly recognized in the pediatric population. They are often characterized by marked genotypic and phenotypic heterogeneity, complicating diagnostic work in clinical practice and molecular diagnosis., Objective: To develop and evaluate a next-generation sequencing panel targeting genes causing neuroinflammation or mimicking neuroinflammation., Design, Setting, and Participants: Cohort study in which a total of 257 genes associated with monogenic neuroinflammation and/or cerebral vasculopathy, including monogenic noninflammatory diseases mimicking these entities, were selected. A customized enrichment capture array, the neuroinflammation gene panel (NIP), was created. Targeted high-coverage sequencing was applied to DNA samples taken from eligible patients referred to Great Ormond Street Hospital in London, United Kingdom, between January 1, 2017, and January 30, 2019, because of onset of disease early in life, family history, and/or complex neuroinflammatory phenotypes., Main Outcomes and Measures: The main outcome was the percentage of individuals with definitive molecular diagnoses, variant classification, and clinical phenotyping of patients with pathogenic variants identified using the NIP panel. The NIP panel was initially validated in 16 patients with known genetic diagnoses., Results: The NIP was both sensitive (95%) and specific (100%) for detection of known mutations, including gene deletions, copy number variants, small insertions and deletions, and somatic mosaicism with allele fraction as low as 3%. Prospective testing of 60 patients (30 [50%] male; median [range] age, 9.8 [0.8-20] years) presenting with heterogeneous neuroinflammatory phenotypes revealed at least 1 class 5 (clearly pathogenic) variant in 9 of 60 patients (15%); 18 of 60 patients (30%) had at least 1 class 4 (likely pathogenic) variant. Overall, a definitive molecular diagnosis was established in 12 of 60 patients (20%)., Conclusions and Relevance: The NIP was associated with molecular diagnosis in this cohort and complemented routine laboratory and radiological workup of patients with neuroinflammation. Unexpected genotype-phenotype associations in patients with pathogenic variants deviating from the classic phenotype were identified. Obtaining an accurate molecular diagnosis in a timely fashion informed patient management, including successful targeted treatment in some instances and early institution of hematopoietic stem cell transplantation in others.

Background: Deficiency of adenosine deaminase 2 (DADA2) is a rare autosomal recessive autoinflammatory condition. Recognised features include vasculitis predominantly affecting medium sized vessels, livedoid skin rash, central and peripheral nervous system involvement, variable degrees of immunodeficiency, and marrow failure, amongst other clinical presentations. We present the case of a six year old male with DADA2 who presented with acute testicular ischaemia secondary to vasculitis, the first such description in DADA2., Case Presentation: A six year old male presented acute right-sided testicular pain. His history included transient infantile neutropenia, resolved hepatosplenomegaly, and longstanding livedo racemosa, leading to screening and confirmation of DADA2 caused by homozygous c.139G > C (p.G47R) mutation of ADA2. As his only clinical feature was that of mild livedo racemosa with normal laboratory parameters at diagnosis, he was being actively monitored prior to starting any treatment. At a routine clinic follow-up a 24 h history of testicular pain was noted on systems review. He was afebrile, and his only physical signs were that of moderate livedo racemosa, and tenderness of the right testicle. Laboratory parameters revealed C-reactive protein (CRP) 8 mg/L (reference range [RR] < 20 mg/L); erythrocyte sedimentation rate (ESR) 28 mm/hr. (RR < 10); and serum amyloid A (SAA)5 mg/L (RR < 10). Ultrasound-scan of the scrotum revealed significantly reduced perfusion of the right testes, without torsion. Surgical scrotal exploration confirmed testicular ischaemia without torsion. Histology demonstrated ischaemic seminiferous tubules with intervening haemorrhage and acute inflammatory cells, consistent with vasculitis of the testis as the cause. He was treated with high dose intravenous methyl-prednisolone followed by a weaning course of oral prednisolone, and subcutaneous adalimumab (anti-tumour necrosis factor alpha, anti-TNFα). Repeat ultrasound-scan 3 weeks later revealed good testicular perfusion, with a small area of focal infarction. At last follow-up (11 months post-event) he remained asymptomatic, on treatment with adalimumab., Conclusion: The phenotype of DADA2 continues to expand, and we add testicular infarction to the features of DADA2. CRP and SAA cannot be relied on as reliable biomarkers to predict tissue ischaemia and hence who to target for anti-TNFα therapy in DADA2, since these remained steadfastly normal before, during, and after testicular infarction in this case.

Coffin-Siris syndrome (CSS) and Nicolaides-Baraitser syndrome (NBS) are 2 overlapping syndromes caused by mutations in genes of the barrier-to-autointegration factor chromatin-remodeling complex, presenting with multiple malformations and intellectual disability. Musculoskeletal changes such as noninflammatory prominence of interphalangeal joints in hands, feet, and, to a lesser extent, knee joints are common in NBS (up to 85%) and also reported in CSS. We present the case of a 7-year-old boy with polyarthritis of several years' duration (without uveitis), developmental delay, microcephaly, and dysmorphic features reminiscent of NBS. Sanger sequencing of the SMARCA2 gene revealed no mutations. Laboratory test results were normal. With synovial biopsy, we confirmed a chronic inflammatory synovitis. Brain MRI revealed dysgenesis of the corpus callosum. Treatment with methotrexate and, subsequently, etanercept led to significant clinical improvement. Whole-exome sequencing revealed a de novo heterozygous nonsense mutation in the ARID1B gene, resulting in a premature stop codon (c.C5404T; p.R1802×), a genotype consistent with CSS. The absence of significantly raised inflammatory markers and a clinical diagnosis of a genetic syndrome associated with noninflammatory joint changes may have contributed to this patient's polyarthritis being missed for several years. We propose that some patients with CSS may have inflammatory arthritis (with or without coexisting skeletal dysplasia), which may be helped by treatment as described herein. Early recognition and treatment of inflammatory arthritis in CSS would have a significant impact on reducing disease burden and improving quality of life for patients with this rare genetic syndrome., Competing Interests: POTENTIAL CONFLICT OF INTEREST: Dr Brogan has received a grant from Novartis, consulting fees from Roche, speaker fees from UCB, committee fees and an institutional grant from Swedish Orphan Biovitrum for gene hunting in autoinflammation, an institutional grant from Novimmune for a clinical trial, and other institutional fees from ChemoCentryx; the other authors have indicated they have no potential conflicts of interest to disclose., (Copyright © 2019 by the American Academy of Pediatrics.)

Competing Interests: Competing interests: None declared.

Objective: The aim was to carry out a retrospective review of the efficacy and safety of anakinra in paediatric patients with undifferentiated autoinflammatory disease (uAID)., Methods: We carried out a retrospective study of children with uAID at a single quaternary centre. The clinical efficacy of anakinra was evaluated using physician global assessment (PGA) and serological response assessed by levels of serum amyloid A and CRP. Safety was assessed by exploring adverse events, including infection and drug reactions., Results: This study included 22 patients, 64% females and 36% males of median age 7.1 years (range 0.13-14.11 years), with uAID. The median starting dose of anakinra was 2 mg/kg (range 2-6 mg/kg) and the median duration of treatment 19.6 months (range 0.8-100 months). Before anakinra treatment, the median PGA, on a three-point Likert scale, was 2 (range 1-2), which fell to 1 (range 0-2) within 3 months of treatment. Eight of 22 (36%) patients achieved complete clinical and serological remission; 8/22 (36%) achieved a partial response; and 6/22 (28%) had no response to anakinra. Adverse events included death (3/22, 14%) and allogeneic haematopoietic stem cell transplantation (1/22, 5%). There were no new safety signals, and anakinra was well tolerated overall., Conclusion: Retrospectively, 72% of children with uAID responded well to anakinra, with 36% achieving full clinical and serological remission within 3 months. This suggests that empirical trials of IL-1 blockade might be warranted in children with uAID. Clear stopping criteria based on predefined parameters should be considered, because non-responders required alternative therapies, facilitated by a definitive molecular diagnosis where possible.

It is now increasingly recognized that some monogenic autoinflammatory diseases and immunodeficiencies cause vasculitis, although genetic causes of vasculitis are extremely rare. We describe a child of non-consanguineous parents who presented with cutaneous vasculitis, digital ischaemia and hypocomplementaemia. A heterozygous p.R1042G gain-of-function mutation (GOF) in the complement component C3 gene was identified as the cause, resulting in secondary C3 consumption and complete absence of alternative complement pathway activity, decreased classical complement activity, and low levels of serum C3 with normal C4 levels. The same heterozygous mutation and immunological defects were also identified in another symptomatic sibling and his father. C3 deficiency due GOF C3 mutations is thus now added to the growing list of monogenic causes of vasculitis and should always be considered in vasculitis patients found to have persistently low levels of C3 with normal C4.

Cutaneous leukocytoclastic vasculitis arises from immune complex deposition and dysregulated complement activation in small blood vessels. There are many causes, including dysregulated host response to infection, drug reactions, and various autoimmune conditions. It is increasingly recognised that some monogenic autoinflammatory diseases cause vasculitis, although genetic causes of vasculitis are extremely rare. We describe a child of consanguineous parents who presented with chronic cutaneous leukocytoclastic vasculitis, recurrent upper respiratory tract infection, and hypocomplementaemia. A homozygous p.His380Arg mutation in the complement factor I (CFI) gene CFI was identified as the cause, resulting in complete absence of alternative complement pathway activity, decreased classical complement activity, and low levels of serum factor I, C3, and factor H. C4 and C2 levels were normal. The same homozygous mutation and immunological defects were also identified in an asymptomatic sibling. CFI deficiency is thus now added to the growing list of monogenic causes of vasculitis and should always be considered in vasculitis patients found to have persistently low levels of C3 with normal C4.

To date, the pathogenic mechanisms underlying Schnitzler syndrome remain obscure, in particular, the interplay between the monoclonal protein and increased interleukin-1β (IL-1β) production, although interest in the contribution of genetic factors has been fueled by detection of somatic NLRP3 mosaicism in 2 patients with the variant-type Schnitzler syndrome. At 2 specialist UK centers, we have identified 21 patients who fulfilled diagnostic criteria for Schnitzler syndrome with urticarial rash, fever, arthralgia, and bone pain; 47% reported weight loss, 40% fatigue, and 21% lymphadenopathy. An immunoglobulin M (IgM) κ paraprotein was detected in 86%; the remainder had IgM λ or IgG κ. Patients underwent searches for germ line and somatic mutations using next-generation sequencing technology. Moreover, we designed a panel consisting of 32 autoinflammatory genes to explore genetic susceptibility factor(s) to Schnitzler syndrome. Genetic analysis revealed neither germ line nor somatic NLRP3 , TNFRSF1A , NLRC4 , or NOD2 mutations, apart from 1 patient with a germ line NLRP3 p.V198M substitution. The proinflammatory cytokines and extracellular apoptosis-associated speck-like protein with caspase recruitment domain (ASC) measured in the serum of Schnitzler syndrome patients during active disease were significantly higher than healthy controls. Ninety-five percent of our cohort achieved a complete response to recombinant IL-1 receptor antagonist (anakinra). Our findings do not support a role for somatic NLRP3 mosaicism in disease pathogenesis; although elevated levels of ASC, IL-6, and IL-18 in patients' serum, and the response to anakinra, suggest that Schnitzler syndrome is associated with upregulated inflammasome activation. Despite its rarity, Schnitzler syndrome is an important diagnosis as treatment with IL-1 antagonists dramatically improves quality of life for patients., (© 2018 by The American Society of Hematology.)

Background: Monogenic autoinflammatory diseases (AID) are a rapidly expanding group of genetically diverse but phenotypically overlapping systemic inflammatory disorders associated with dysregulated innate immunity. They cause significant morbidity, mortality and economic burden. Here, we aimed to develop and evaluate the clinical impact of a NGS targeted gene panel, the "Vasculitis and Inflammation Panel" (VIP) for AID and vasculitis., Methods: The Agilent SureDesign tool was used to design 2 versions of VIP; VIP1 targeting 113 genes, and a later version, VIP2, targeting 166 genes. Captured and indexed libraries (QXT Target Enrichment System) prepared for 72 patients were sequenced as a multiplex of 16 samples on an Illumina MiSeq sequencer in 150bp paired-end mode. The cohort comprised 22 positive control DNA samples from patients with previously validated mutations in a variety of the genes; and 50 prospective samples from patients with suspected AID in whom previous Sanger based genetic screening had been non-diagnostic., Results: VIP was sensitive and specific at detecting all the different types of known mutations in 22 positive controls, including gene deletion, small INDELS, and somatic mosaicism with allele fraction as low as 3%. Six/50 patients (12%) with unclassified AID had at least one class 5 (clearly pathogenic) variant; and 11/50 (22%) had at least one likely pathogenic variant (class 4). Overall, testing with VIP resulted in a firm or strongly suspected molecular diagnosis in 16/50 patients (32%)., Conclusions: The high diagnostic yield and accuracy of this comprehensive targeted gene panel validate the use of broad NGS-based testing for patients with suspected AID.