Search

Deficiency of adenosine deaminase 2 (DADA2) is a unique monogenic autoinflammatory disease caused by autosomal recessive loss-of-function mutations in the CECR1 gene which presents as childhood-onset small- and medium-vessel vasculitis. Previously, many of these patients were misdiagnosed and thought to have clinical features of systemic polyarteritis nodosum, which negatively influenced its outcome, since TNF inhibitors seem to have efficacy on the vasculitic phenotype of DADA2. We present a case of a 28-year-old woman with a lifelong unknown syndrome and unique clinical manifestations recently recognized as DADA2. The first manifestation, at 3 months of age, was an episode of facial paralysis during which renovascular hypertension was diagnosed. Later, she developed episodes of prolonged fever, polyarthritis, Raynaud’s phenomenon, gastrointestinal bleeding, and intracerebral hemorrhage. This inflammatory state ultimately led to the development of amyloid A amyloidosis and renal insufficiency.

Background Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive inflammatory disease caused by loss-of-function mutations in both alleles of the ADA2 gene. Most patients with DADA2 exhibit systemic vasculopathy consistent with polyarteritis nodosa, but large phenotypic variability has been reported, and the pathogenesis of DADA2 remains unclear. Objectives This study sought to assess the clinical and genetic characteristics of Japanese patients with DADA2 and to gain insight into the pathogenesis of DADA2 by multi-omics analysis. Methods Clinical and genetic data were collected from 8 Japanese patients with DADA2 diagnosed between 2016 and 2019. ADA2 variants in this cohort were functionally analyzed by in vitro overexpression analysis. PBMCs from 4 patients with DADA2 were subjected to transcriptome and proteome analyses. Patient samples were collected before and after introduction of anti- TNF-α therapies. Transcriptome data were compared with those of normal controls and patients with other autoinflammatory diseases. Results Five novel ADA2 variants were identified in these 8 patients and were confirmed pathogenic by in vitro analysis. Anti-TNF-α therapy controlled inflammation in all 8 patients. Transcriptome and proteome analyses showed that upregulation of type II interferon signaling was characteristic of DADA2. Network analysis identified STAT1 as a key regulator and a hub molecule in DADA2 pathogenesis, a finding supported by the hyperactivation of STAT1 in patients’ monocytes and B cells after IFN-γ stimulation. Conclusions Type II interferon signaling and STAT1 are associated with the pathogenesis of DADA2.

Introduction: Deficiency of Adenosine deaminase 2 (DADA2) is a monogenic autoinflammatory disorder presenting a broad spectrum of clinical manifestations, including vasculitis, immunodeficiency and hematologic disease. The genetic mutations in ADA2 gene have been associated to an insufficient ADA2 activity leading to reduction in deamination of adenosine to deoxyadenosine, and a consequent accumulation of extracellular adenosine. The pathogenic mechanisms investigated so far have elucidated a skewed polarization from the M2 macrophage subtype to the proinflammatory M1 subtype with an increased production of inflammatory cytokines (TNF-?, Interferon IFN). More recently a chronic neutrophil activation and a dysregulation of NETosis, as process triggered by extracellular Adenosine, inducing TNF? secretion from Macrophages stimulated by NETs, has been implicated in the pathogenesis of DADA2. Objectives: The aim of the project is to dissect NETosis directly in neutrophils isolated from DADA2 patients and healthy controls (HDs), and to quantify suicidal and vital NETosis induced by several stimuli. To determine if NET epitopes can change depending from the inflammatory microenvironment and if protein composition of NETs is disease specific, we used quantitative proteomics approach to characterize NET proteins, released from neutrophils after different stimuli in DADA2 patients, HDs and nongenetic vasculitis. Moreover, we investigated the mechanisms of NETs removal. To verify if NETs can influence maturation or inflammatory phenotype of DCs, we characterized peripheral myeloid Dendritic cells (mDCs) and plasmocytoid DCs (pDC) in DADA2 patients and analyzed in vitro moDC maturation and cytokine production in presence of NETs. Methods: We analyzed and quantified both suicidal and vital NETosis by Imaging Flow Citometry (IFC): neutrophils isolated from peripheral blood from DADA2 patients and HDs were stimulated in vitro with different stimuli (PMA, Adenosine and LPS) to induce NETosis and were analyzed in the ImageStreamXMark II IFC equipped with a MultiMag system. We evaluated also NETs remnants and DNAse in the plasma samples by ELISA assay. We used quantitative proteomics approach to characterize NET proteins, released from neutrophils after different stimuli in DADA2 patients, HDs and nongenetic vasculitis: LC-MS/MS analyses were conducted on Orbitrap Fusion Tribrid mass spectrometer and NET protein quantification was carried out using Label-Free Quantification method. We isolated monocytes from peripheral blood with microbeads and we generated moDC after culture stimulation with LPS/NETs. On the 7th day we analyzed by flow cytometry the phenotype and the markers of differentiation. Quantification of cytokines was performed by flow cytometry bead array. Results: We enrolled 14 patients with Adenosine Deaminase 2 deficiency diagnosis who underwent blood sampling at out Center, collecting also plasma samples from further 6 genetically confirmed DADA2 patients enrolled by other Italian Pediatric Rheumatology Units. Neutrophils from DADA2 show a significant increased suicidal NETosis, identified as nuclear decondensation and Myeloperoxidase (MPO) colocalization with DNA, following PMA stimulation and we observed an increase also with LPS and Adenosine. Then we analyzed vital NETosis, identified as elongated shape of cells, nuclei polarized within the cell and not colocalized with MPO and we found an increased vital NETosis in DADA2 neutrophils. Accordingly, plasmatic levels of circulating nucleosomes (NET remnants) were elevated in patients; DNAse levels were normal but the activity was reduced. We set up experimental conditions for proteomic analysis of NETs, induced by PMA, Adenosine and TNF?, testing two patients, two HDs and two patients with non-genetic vasculitis: in total we identified 1770 proteins among which a hundred of proteins were significantly up or down-modulated in DADA2 NETs compared to controls NETs. DC phenotype in DADA2 patients result concordant with HD, as well as moDCs cytokine production after LPS stimulation. We observed a stimulatory effect of NETs towards induction of TNF alpha, IL-6 production and IP-10 from moDCs in both HD and DADA2. Conclusion: Our findings confirm a dysregulation in NETosis process in DADA2 patients, that can be induced by both LPS and adenosine. An increase of vital NETosis was also identified. Proteomic profile of NETs isolated from DADA2 is different from HD and PAN patients: NETs are qualitatively different between HD and DADA2. NETs in DADA2 may therefore interact differently with innate immunity compartment, stimulating DCs to produce citokines, contributing to the typical inflammatory phenotype.

SUMMARY: Adenosine deaminase 2 deficiency (OMIM #615688) is an autosomal recessive disorder characterized by a wide clinical spectrum, including small- and medium-sized vessel vasculopathies, but data focusing on the associated neuroimaging features are still scarce in the literature. Here, we describe the clinical neuroimaging features of 12 patients with genetically proven adenosine deaminase 2 deficiency (6 males; median age at disease onset, 1.3 years; median age at genetic diagnosis, 15.5 years). Our findings expand the neuroimaging phenotype of this condition demonstrating, in addition to multiple, recurrent brain lacunar ischemic and/or hemorrhagic strokes, spinal infarcts, and intracranial aneurysms, also cerebral microbleeds and a peculiar, likely inflammatory, perivascular tissue in the basal and peripontine cisterns. Together with early clinical onset, positive family history, inflammatory flares and systemic abnormalities, these findings should raise the suspicion of adenosine deaminase 2 deficiency, thus prompting genetic evaluation and institution of tumor necrosis factor inhibitors, with a potential great impact on neurologic outcome.

Adenosine deaminase 2 deficiency (DADA2) is an autoinflammatory disease characterized by inflammatory vasculopathy, early strokes associated often with hypogammaglobulinemia. Pure red cell aplasia, thrombocytopenia, and neutropenia have been reported. The defect is due to biallelic loss of function of ADA2 gene, coding for a protein known to regulate the catabolism of extracellular adenosine. We therefore investigated immune phenotype and B- and T-cell responses in 14 DADA2 patients to address if ADA2 mutation affects B- and T-cell function. Here, we show a significant decrease in memory B cells, in particular class switch memory, and an expansion of CD21low B cells in DADA2 patients. In vitro stimulated B lymphocytes were able to secrete nonfunctional ADA2 protein, suggesting a cell intrinsic defect resulting in an impairment of B-cell proliferation and differentiation. Moreover, CD4+ and CD8+ T cells were diminished; however, the frequency of circulating T follicular helper cells was significantly increased but they had an impairment in IL-21 production possibly contributing to an impaired B cell help. Our findings suggest that ADA2 mutation could lead to a B-cell intrinsic defect but also to a defective Tfh cell function, which could contribute to the immunodeficient phenotype reported in DADA2 patients.

Adenosine deaminase 2 deficiency (DADA2) is a rare inherited disorder that is caused by autosomal recessive mutations in the ADA2 gene. Clinical manifestations include early-onset lacunar strokes, vasculitis/vasculopathy, systemic inflammation, immunodeficiency, and hematologic defects. Anti–tumor necrosis factor therapy reduces strokes and systemic inflammation. Allogeneic hematopoietic stem/progenitor cell (HSPC) transplantation can ameliorate most disease manifestations, but patients are at risk for complications. Autologous HSPC gene therapy may be an alternative curative option for patients with DADA2. We designed a lentiviral vector encoding ADA2 (LV-ADA2) to genetically correct HSPCs. Lentiviral transduction allowed efficient delivery of the functional ADA2 enzyme into HSPCs from healthy donors. Supranormal ADA2 expression in human and mouse HSPCs did not affect their multipotency and engraftment potential in vivo. The LV-ADA2 induced stable ADA2 expression and corrected the enzymatic defect in HSPCs derived from DADA2 patients. Patients’ HSPCs re-expressing ADA2 retained their potential to differentiate into erythroid and myeloid cells. Delivery of ADA2 enzymatic activity in patients’ macrophages led to a complete rescue of the exaggerated inflammatory cytokine production. Our data indicate that HSPCs ectopically expressing ADA2 retain their multipotent differentiation ability, leading to functional correction of macrophage defects. Altogether, these findings support the implementation of HSPC gene therapy for DADA2.

Adenosine Deaminase 2 Deficiency (DADA2) (OMIM: 607575) is a monogenic, autoinflammatory disease caused by the loss of functional homozygous or heterozygous mutations in the ADA 2 gene (previously CECR1, Cat Eye Syndrome Chromosome Region 1). A timely diagnosis is crucial to start Anti-TNF therapies that are efficacious in controlling the disease. The confirmation of DADA2 is based on DNA sequencing and enzymatic assay. It is, thus, very important to have robust and reliable assays that can be rapidly utilized in specialized laboratories that can centralize samples from other centers. In this paper, we show a novel enzymatic assay based on liquid chromatography-tandem mass spectrometry that allows the accurate determination of the ADA2 enzyme activity starting from very small amounts of plasma spotted on filter paper (dried plasma spot). The method allows significantly distinguishing healthy controls from affected patients and carriers and could be of help in implementing the diagnostic workflow of DADA2.

Adenosine Deaminase 2 Deficiency (DADA2) syndrome is a rare monogenic disorder prevalently linked to recessive inherited loss of function mutations in the ADA2/CECR1 gene. It consists of an immune systemic disease including autoinflammatory vasculopathies, with a frequent onset at infancy/early childhood age. DADA2 syndrome encompasses pleiotropic manifestations such as stroke, systemic vasculitis, hematologic alterations, and immunodeficiency. Although skeletal abnormalities have been reported in patients with this disease, clear information about skeletal health, with appropriate biochemical-clinical characterization/management, its evolution over time and any appropriate clinical management is still insufficient. In this paper, after a general introduction shortly reviewing the pathophysiology of Ada2 enzymatic protein, its potential role in bone health, we describe a case study of two 27 year-old DADA2 monozygotic female twins exhibiting bone mineral density and bone turnover rate abnormalities over the years of their clinical follow-up.

Purpose Deficiency of adenosine deaminase 2 (DADA2) is an inherited inborn error of immunity, characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure (BMF). Tumor necrosis factor (TNF-α) blockade is the treatment of choice for the vasculopathy, but often fails to reverse refractory cytopenia. We aimed to study the outcome of hematopoietic cell transplantation (HCT) in patients with DADA2. Methods We conducted a retrospective study on the outcome of HCT in patients with DADA2. The primary outcome was overall survival (OS). Results Thirty DADA2 patients from 12 countries received a total of 38 HCTs. The indications for HCT were BMF, immune cytopenia, malignancy, or immunodeficiency. Median age at HCT was 9 years (range: 2–28 years). The conditioning regimens for the final transplants were myeloablative (n = 20), reduced intensity (n = 8), or non-myeloablative (n = 2). Donors were HLA-matched related (n = 4), HLA-matched unrelated (n = 16), HLA-haploidentical (n = 2), or HLA-mismatched unrelated (n = 8). After a median follow-up of 2 years (range: 0.5–16 years), 2-year OS was 97%, and 2-year GvHD-free relapse-free survival was 73%. The hematological and immunological phenotypes resolved, and there were no new vascular events. Plasma ADA2 enzyme activity normalized in 16/17 patients tested. Six patients required more than one HCT. Conclusion HCT was an effective treatment for DADA2, successfully reversing the refractory cytopenia, as well as the vasculopathy and immunodeficiency. Clinical Implications HCT is a definitive cure for DADA2 with > 95% survival.

Deficiency of human adenosine deaminase 2 (DADA2) is an auto-inflammatory inborn error of immunity caused by biallelic deleterious mutations in the gene encoding ADA2. The purpose of this article is to raise awareness among ophthalmologists and pediatricians to consider DADA2 as a possible diagnosis for patients with acute onset of diplopia. The authors describe two pediatric patients who presented with double vision due to uni-lateral adduction deficit, and discuss the importance of recognizing this clinically as an ophthalmologist. If a child presents with a sudden eye movement abnormality, ophthalmologists must be aware of the possibility of an ischemic insult due to an underlying genetic disorder (eg, DADA2), especially in patients with a positive familial history or associated clinical signs such as a personal history of characteristic skin lesions or paresis of other cranial nerves. Given the multi-organ involvement in this disorder, a multi-disciplinary approach is crucial to have a timely diagnosis and to treat this rare disorder appropriately. [ J Pediatr Ophthalmol Strabismus . 2021;58(4):e22–e26.]

Deficiency of adenosine deaminase 2 (DADA2) is a rare recessive disorder caused by the bi-allelic loss-of-function pathogenic variants in the ADA2 gene (MIM: 607575, also known as CECR1, cat eye syndrome chromosome region, candidate 1). Based on the Human Gene Mutation Database (HGMD®), 53 different disease-causing variants have been identified in this gene to date. This case report aims to describe a new vasculitis, autoinflammation, immunodeficiency, and hematologic defects syndrome (VAIHS) case caused by a novel pathogenic variant. A four-year-old boy was referred to our hospital with anemia, thrombocytopenia, and stroke, but no skin manifestations. The patient had a significant phenotypic overlap with VAIHS. Molecular genetic analysis via whole exome sequencing identified a homozygous deleterious variant in ADA2. To our knowledge, the identified variant has never been described in the literature. Screening for ADA2 pathogenic variants should be considered in the differential diagnosis of pediatric patients manifesting with chronic thrombocytopenia or early-onset stroke for an accurate diagnosis and appropriate treatment choices.

Objective.Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disorder associated with ADA2 mutations. We aimed to investigate the characteristics and ADA2 enzyme activities of patients with DADA2 compared to non-DADA2 patients.Methods.This is a descriptive study of 24 patients with DADA2 who were admitted to the Adult and Pediatric Rheumatology, Pediatric Haematology, and Pediatric Immunology Departments of Hacettepe University. All ADA2 exons were screened by Sanger sequencing. Serum ADA2 enzyme activity was measured by modified spectrophotometric method.Results.Twenty-four patients with DADA2 were included: 14 with polyarteritis nodosa (PAN)-like phenotype (Group 1); 9 with Diamond-Blackfan anemia (DBA)-like features, and 1 with immunodeficiency (Group 2). Fourteen PAN-like DADA2 patients did not have the typical thrombocytosis seen in classic PAN. Inflammatory attacks were evident only in Group 1 patients. Serum ADA2 activity was low in all patients with DADA2 except one, who was tested after hematopoietic stem cell transplantation. There was no significant difference in ADA2 activities between PAN-like and DBA-like patients. In DADA2 patients with one ADA2 mutation, serum ADA2 activities were as low as those of patients with homozygote DADA2. ADA2 activities were normal in non-DADA2 patients. ADA2 mutations were affecting the dimerization domain in Group 1 patients and the catalytic domain in Group 2 patients.Conclusion.We suggest assessing ADA2 activity along with genetic analysis because there are patients with one ADA2 mutation and absent enzyme activity. Our data suggest a possible genotype–phenotype correlation in which dimerization domain mutations are associated with PAN-like phenotype, and catalytic domain mutations are associated with hematological manifestations.

Background Deficiency of adenosine deaminase 2 (DADA2) is a recessively inherited autoinflammatory disorder caused by a loss of functional ADA2 protein. TNF inhibition (TNFi) has proven to be highly effective in treating inflammatory manifestations. Objective To explore the pathophysiology and the underlying mechanisms of TNF inhibitor response in these patients. Methods We performed Sanger sequencing of the ADA2 gene. We used flow cytometry, intracellular cytokine staining, transcriptome analysis, immunohistochemistry, and cell differentiation experiments to define an inflammatory signature in DADA2 patients and studied their response to TNF inhibitor treatment. Results We demonstrated increased inflammatory signals and overproduction of cytokines mediated by IFN and NF-κB pathways in patients’ primary cells. Treatment with TNFi led to reduction in inflammation, rescued the skewed differentiation towards the pro-inflammatory M1 macrophage subset and restored integrity of endothelial cells in blood vessels. We also report 8 novel disease-associated variants in 7 patients with DADA2. Conclusion Our data explore the cellular mechanism underlying effective treatment with TNFi therapies in DADA2. DADA2 vasculitis is strongly related to the presence of activated myeloid cells and the endothelial cell damage is rescued with anti-TNF treatment.

Polyarteritis nodosa (PAN) is a rare systemic necrotizing vasculitis predominantly affecting the medium-sized arteries with widely variable presenting features, disease course, and outcomes. Recent updates regarding the nomenclature of PAN have resulted in the description of several PAN sub-phenotypes. Herein discussed are idiopathic PAN, Hepatitis B-associated PAN and monogenic disorders such as adenosine deaminase-2 deficiency. The current understanding of the pathogenesis, histopathological features, and treatment of these conditions are reviewed.

Background Two brothers, both with past history of early-onset strokes (bilateral thalamic infarcts aged 6 years in one and left mid brain infarct aged 4 in other) were referred to the neurology and genetics service. Investigation releveled iron refractory anaemia (subsequently managed by haematology) and isodisomy for chromosome 22. Both made a good neurological recovery and were commenced on daily aspirin. Gene CECR1 was considered but dismissed due to no reported myalgia, fever or skin rash. Five years after initial referral whole genome sequencing revealed a homozygous mutation in the adenosine deaminase 2 gene (CECR1). Both brothers were diagnosed with adenosine deaminase 2 deficiency (DADA2) and referred to paediatric rheumatology. Review of previous investigations revealed persistently raised inflammatory markers. Hepatosplenomegaly was present in both and lymphadenopathy and ear symptoms in younger brother on initial rheumatology review. Mutations in the CECR1 gene prevent it correctly encoding the enzyme Adenosine Deaminase 2. This is a growth factor for endothelial cells and promotes the differentiation of M2 macrophages. Deficiency results in decreased vascular integrity, a predominance of proinflammatory macrophages and perivascular inflammation medicated by tumour necrosis factor (TNF). Methods A literature review was carried out to determine evidence of treatment for this rare condition. Results DADA2 is currently extremely rare with only 200 cases reported in the literature. Small studies have found anti-TNF medication to be beneficial in reducing glucocorticoid use and preventing further neurological events. There are case reports of successful allogeneic hematopoietic stem-cell transplantation but concerns remain that associated vascular problems may increase the risk of serious side effects. Conclusion Following literature review an internal funding request for Adalimumab was accepted and both boys commenced anti-TNF treatment. We present a case of two brothers with this recently discovered monogenic systemic vasculopathy, now recognised to show huge clinical diversity even among family members with identical mutations. Immunodeficiency and haematological features are commonly reported but awareness across all specialties is needed. It is currently unknown how defects in a single gene results in these heterogeneous presentations. It is hoped that gene therapy will provide a cure for this condition in the future.

Deficiency of Adenosine deaminase 2 (DADA2) syndrome is a chronic, systemic, and inflammatory disorder, characterized by early-onset recurrent strokes, fever, livedo reticularis, and immunodeficiency. We report the case of a 4-year-old child, a product of consanguineous marriage, who presented with three episodes of hemiparesis within 1 year. She also manifested skin discoloration in the form of livedo reticularis. Workup with magnetic resonance imaging (MRI) of the brain revealed acute infarction in the right aspect of the cerebral peduncle and chronic lacunars infarct in the right thalamus with diffusion restriction. Repeated MRI after 5 months revealed diffuse loss of brain volume. The blood workup showed high inflammatory markers and significantly low adenosine deaminase 2 (ADA2) level. After being on corticosteroid and anticoagulant treatments, she suffered from a recurrent episode of cerebral infarction, after which she was commenced on tumor necrosis factor (TNF)-antagonist therapy in addition to monthly fresh plasma infusion. Thereafter, there was no cerebral insult reported for >18 months. The genetic study of the child and her parents revealed a homozygous mutation c. 336C>A, p. (His112Gln) in the CECR1 gene, and her parents were heterozygous for the same variant. This variant was not previously reported in literature. We would suggest linking this novel variant c. 336C>A, p. (His112Gln) of CECR1 gene mutation with the clinical picture, along with the positive response to TNF-antagonist therapy in the era of ADA2 deficiency syndrome.

Purpose of Review We aim to describe the pathophysiology, clinical findings, diagnosis, and treatment of deficiency of adenosine deaminase 2 (DADA2). Recent Findings DADA2 is a multi-organ disease of children and less often adults, which can present with wide-ranging manifestations including strokes, medium vessel vasculitis, hematologic disease, and immunodeficiency. Diagnosis is through detection of reduced activity level of the adenosine deaminase 2 (ADA2) enzyme and/or identification of bi-allelic mutations in the ADA2 gene. Outside of high-dose glucocorticoids, conventional immunosuppression has been largely ineffective in treating this relapsing and remitting disease. Vasculitic-predominant manifestations respond extremely well to tumor necrosis factor-α inhibition. Hematopoietic stem cell transplantation can lead to normalization of enzyme activity, as well as resolution of vasculitic, hematologic, and immunologic manifestations, although treatment-related adverse effects are not uncommon. Summary Early detection of this disease across multiple disciplines could prevent devastating clinical outcomes, especially in genetically pre-disposed populations.

Background Deficiency of adenosine deaminase 2 (DADA2) is a rare autoinflammatory disease caused by mutations in the ADA2 gene. Few Chinese cases have been reported. We describe and compare the clinical features, genotypes, and treatments of Chinese DADA2 patients and non-Chinese patients. Methods Primary immunodeficiency disease panel or whole-exome sequencing was performed for suspected cases, and assays for adenosine deaminase 2 (ADA2) enzyme activity were also carried out for the patients and their parents. Case reports of Chinese and non-Chinese patients with DADA2 were searched in PubMed and Chinese national databases. Results Seven unrelated children from China with DADA2 were included in our study. Five were identified at Peking Union Medical College Hospital, and two had been reported previously (1 on PubMed and 1 in Chinese literature). Fourteen mutations in ADA2 were identified, 7 of which have not previously been reported in non-Chinese patients. Four children who underwent enzymatic analysis had lower ADA2 activity compared with their parents. Phenotypic manifestations included fever, skin symptoms, vasculitis, and neurologic involvement. Treatments varying from steroids, immunosuppressants, and tocilizumab, anti-TNF therapy and hematopoietic stem cell transplantation (HSCT) were effective depending on phenotype and severity. Conclusion This study includes the largest number of Chinese DADA2 patients to date. We recommend the combination of enzymatic analysis with gene screening to confirm the diagnosis. Different genotypes were observed among Chinese DADA2 patients; most phenotypes were similar to those of non-Chinese DADA2 patients, except for growth retardation. Disease remission might not be achieved with anti-IL-6 therapy.

Rheumatic diseases usually have very diverse and complex pathophysiology resulting in different clinical phenotypes. Some certain phenotypes cluster together with a common presentation, course, and outcome. Our primary aim is to review the known disease clusters in certain rheumatological conditions. Cluster analysis has been reported in several rheumatic diseases, Behcet disease being the most common. Five individual clusters together with some clinical associations have been reported in Behcet patients. Certain antibody-phenotype associations and damage clusters have been reported in systemic lupus erythematosus (SLE) patients as well. Although there is no proper cluster analysis, two distinct phenotypes are evident in deficiency of ADA2 (DADA2): those with a polyarteritis nodosa-like vasculopathy and hematological involvement with pure red cell aplasia or bone marrow failure. The variants are claimed to be different regions of this gene for these 2 phenotypes. Lastly, there is a recent paper grouping ANCA-associated vasculitis according to disease phenotype and antibody associations. There are distinct clusters in certain rheumatic diseases which might help us to predict comorbidities, disease course, and treatment response.

Background/purpose To assess EDI-OCT (enhanced depth imaging optical coherence tomography) of choroid for inflammatory signs in children with polyarteritis nodosa (PAN) and adenosine deaminase-2 deficiency (DADA-2). Methods In this cross-sectional study conducted between June 2017 and September 2018, we evaluated children diagnosed with PAN (n = 11) and DADA-2 (n = 4) and an age- and sex-matched control group (n = 15). Demographic and laboratory data were retrospectively analyzed from patient charts. Disease activity was assessed using the pediatric vasculitis activity score (PVAS). Choroidal images were obtained with spectral domain-OCT to measure choroidal thickness (ChT) at 5 points (750 and 1500 μm from the foveal center in the temporal and nasal quadrants and beneath the fovea), and to calculate the total subfoveal choroidal area (TCA), luminal area (LA), stromal area (SA), and the choroidal vascularity index (CVI). Results The median (min-max) age was 8 (4–16) years in PAN patients, 6 (5–16) years in DADA-2 patients and 8 (8–10) years in control group at the OCT visit (p = 0.214). The ChT at 3 points and the TCA, LA, and SA were higher in children with both PAN and DADA-2 patients compared to those of the control group (p p = 0.049, p = 0.007, p = 0.007, p = 0.006, p = 0.033, respectively). The CVI was similar in both groups. No association was observed between the OCT findings, PVAS, and the erythrocyte sedimentation rate, and serum leukocyte and C-reactive protein levels. Conclusion Similar CVI scores were obtained from PAN and DADA2 patients under treatment and from healthy controls. Increased subfoveal ChT without any other signs of ocular involvement may suggest choroidal thickening as a sign of mild subclinical inflammation.

OBJECTIVE: To develop a set of clinical criteria that identifies patients with a potential autoinflammatory IFNopathy. METHODS: Based on a literature review, a set of clinical criteria identifying genetically confirmed monogenic IFNopathies was selected. For validation, the clinical score was assessed in healthy controls (HCs) and 18 disease controls, including 2 known autoimmune IFNopathies, juvenile systemic lupus erythematosus (JSLE, n = 4) and dermatomyositis (JDM, n = 4); adenosine deaminase 2 deficiency (DADA2, n = 4); and oligoarticular juvenile idiopathic arthritis (oJIA, n = 6). We assessed an IFN score (IRG-S) in whole blood by NanoString using a previously published 28-gene-IRG-S and a reduced 6-gene-IRG-S. RESULTS: The 12 patients with a possible IFNopathy had higher clinical scores (3–5) than the patients with sJLE, JDM, DADA2, and oJIA and in HCs. Both the 28-IRG-S and 6-IRG-S were significantly higher in the autoinflammatory IFNopathy patients compared to HCs and oJIA and DADA2 patients but not different from patients with JSLE and JDM. Subsequently, genetic analysis revealed mutations in genes previously reported in genes related to the IFN pathway in 9 of the 12 patients. CONCLUSION: We developed a clinical score to identify patients with possible autoinflammatory IFNopathies. A clinical score was associated with a high IRG-S and may serve to identify patients with an autoinflammatory IFNopathy.

Adenosine deaminase 2 deficiency (DADA2) is a recently defined inborn error of immunity caused by loss-of-function mutations in the ADA2 gene. Patients suffer from severe manifestations, including early-onset lacunar strokes, intracranial hemorrhages, vasculitis/vasculopathy, systemic inflammation, immunodeficiency, and hematologic abnormalities. The therapeutic benefit of the current treatments is unsatisfactory. Anti-tumor necrosis factor therapy reduces strokes and systemic inflammation but does not correct cytopenia and bone marrow failure. Allogeneic hematopoietic stem/progenitor cell (HSPC) transplantation can ameliorate most disease manifestations, but patients are at risk for complications. Therefore, we proposed that autologous HSPC gene therapy may be an alternative curative option for patients who has no compatible donor or cannot receive intense chemotherapy. We performed an in-depth study, using multiparametric flow cytometry, of the bone marrow (BM) cell composition of three adult patients with the hematological phenotype of DADA2. Compared with healthy donors (HDs), patients' BM exhibited a reduced number of mature and immature populations belonging to different hematopoietic lineages. Patients exhibited a substantial reduction in circulating neutrophils and hematopoietic stem cells and progenitor pools in the BM. Severe neutropenia and HSPC defects are direct causes of DADA2. Indeed, ADA2 knock-down in zebrafish - as rodents do not harbor an ADA2 orthologue gene - caused a significant decrease in neutrophil and HSPC numbers, reminiscent of patients' phenotype. Administration of human recombinant ADA2 effectively corrected both neutropenia and defective hematopoiesis in the zebrafish embryo. We used a third-generation LV to restore constitutive ADA2 expression in HSPCs. Transduction of healthy donors' HSPCs allowed efficient delivery of the functional ADA2 enzyme with no toxicity. Supranormal ADA2 expression in healthy donors' and patients' HSPCs was well-tolerated and did not impact HSPC multilineage differentiation potential in vitro and in vivo. We also assessed whether LV-derived ADA2 could correct the hyperinflammatory M1 macrophage phenotype characteristic of DADA2. ADA2 reconstitution in patients' macrophages led to the normalization of IL-6 and TNF release. Similar results were obtained using M1 macrophages differentiated from ADA2-transduced HSPCs. Altogether, our findings indicate that HSPC gene therapy is a promising approach to re-establish stable ADA2 activity and correct the hematological and inflammatory manifestations in patients with DADA2. Disclosures Aiuti: Orchard Therapeutics: Other: PI of clinical trials sponsored by company.

Background Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by mutations in the adenosine deaminase 2 (ADA2) gene. Loss of functional ADA2 activity results in vasculitis syndrome, immunodeficiency, and hematopoietic disorders. Early diagnosis is required for effective treatment. Methods We developed a dried blood spot (DBS)-based ADA2 activity colorimetric assay. Heparin-affinity purification was used during sample preparation to improve the assay more efficiently. The stability of ADA2 during DBS storage and ADA2 activity of DADA2 patients and healthy controls were examined. Results Active ADA2 was extracted from the DBS of healthy controls. ADA2 activity in DBS, stored either frozen or refrigerated, remained stable for at least 90 days. A significant difference in ADA2 activity was observed between healthy controls and patients. No ADA2 activity was detected in DBS from patients. Conclusions Our new DBS ADA2 activity assay is experimentally simple, highly adaptable, and requires no special equipment except for a microplate reader. A low background was achieved with heparin-affinity purification. The method differentiates clearly between healthy controls and patients. ADA2 activity can be reliably measured in DBS, providing an opportunity to diagnose DADA2 at an early stage.

Primary progress has been made in the last 2 years, particularly in finding novel disease-causing genes for a number of autoinflammatory diseases and primary immunodeficiencies. Whole-exome sequencing has dramatically increased the pace at which causative genes are being discovered. CECR1 (Cat eye syndrome chromosome region, candidate 1) gene encodes adenosine deaminase 2 (ADA2) protein. Patients who carry CECR1 mutation(s) suffer from deficiency of ADA2 (DADA2). Here, we describe a patient with pure red cell aplasia discovered to have DADA2. We also review the literature on DADA2. This report will help raise awareness of physicians for this complex disease.

Adenosine deaminase 2 deficiency is an autoinflammatory disease, characterized by various forms of vasculitis. We describe 5 patients with adenosine deaminase 2 deficiency with various hematologic manifestations, including pure red cell aplasia, with no evidence for vasculitis.

Background DADA2 is an autoinflammatory disease with autosomal recessive inheritance characterized by a heterogeneous clinical phenotype ranging from multisystemic inflammation (fever, polyarteritis nodosa, cerebral stroke, livedo reticularis etc.) to immune-dysregulation and immunodeficiency. Objectives To extend the clinical spectrum of DADA2 reporting a case of isolated nonspecific systemic inflammatory syndrome associated with signs of immune-dysregulation in a patient with a novel ADA2 mutation. Methods In a patient with nonspecific inflammatory phenotype associated to susceptibility to viral infections, Next Generation Sequencing (NGS) panel was performed; mutations detected were confirmed by Sanger analysis. ADA2 enzymatic activity was analyzed in monocyte isolated from the patient and incubated with adenosine and an ADA1 inhibitor. Results The girl, adopted and of Asian origin, began to suffer from nonspecific systemic inflammatory symptoms (persistent fever and arthralgias) at the age of 6. In past history recurrent respiratory infections and impaired immunological response to viruses (CMV related hepatitis, measles after vaccination) were reported. After few months the patient developed clinical and laboratory findings of HLH (Hemophagocytic Lympho-Histocytosis), confirmed on bone marrow samples; treatment with intravenous (IV) high dose (HD) steroids was started, with prompt response. During steroids tapering fever and systemic inflammation reappeared; anti-IL1 treatment (anakinra) was not effective. Immunologic assessment demonstrated mild hypogammaglobulinemia and moderate NK deficiency on lymphocyte subsets. HD IV Immunoglobulins (IG) (2 g/kg every month) allowed to achieve a complete control of the clinical picture; the frequency of administration was progressively reduced to every 4 months due to persistent wellbeing. At the age of 9, after switching IG to the substitutive dosage, the patient experienced Herpes Zoster virus reactivation (requiring prolonged antiviral treatment), followed by the reappearance of the inflammatory phenotype complicated by HLH with neurological involvement (irritability and lethargy), responsive to HD steroids and IG. A later cerebral MRI evidenced a small gliotic area in left Centrum Ovale. After steroids suspension, monthly HD IV IG administrations maintained clinical remission. Further immunological studies confirmed a reduction of NK cells with normal function. Hereditary HLH, Autoimmune Lympho-Proliferative Syndrome (ALPS) and main primary immunodeficiencies were ruled out. Given the clinical picture, a large NGS diagnostic panel (courtesy by K. Botzug, Vienna) for autoinflammatory diseases and immunodeficiencies was performed revealing the homozygous LEU141PRO ADA2 mutation, confirmed by Sanger analysis. Being this mutation novel, an ADA2 enzymatic activity test was performed revealing a complete loss of ADA2 activity. The parents refused anti-TNF treatment and the patient is still on monthly HD IG with a complete wellbeing after 3 years of follow-up. Conclusion The current report enlarges the clinical spectrum associated with DADA2 to a persistent unspecific inflammatory syndrome, complicated by HLH. This case further emphasizes the possibility that NGS could unravel unusual phenotypes of already known inflammatory syndromes. Even if further reports are required, the response to HD IG observed in the present case it is of interest. Even if anti-TNF is the treatment of choice HD IG could be a possible treatment in DADA2, especially during the acute phase. References [1] Caorsi R, et al. Ann Rheum Dis. 201776(10):1648-1656 Disclosure of Interests Francesca Garbarino: None declared, Roberta Caorsi: None declared, Stefano Volpi: None declared, Alice Grossi: None declared, Isabella Ceccherini: None declared, Marco Gattorno Grant/research support from: MG has received unrestricted grants from Sobi and Novartis