Treatment Strategies for Deficiency of Adenosine Deaminase 2

A case report on deficiency of adenosine deaminase 2 with relapse-remission course and analysis of genotype-phenotype correlation

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic disease caused by biallelic mutations in adenosine deaminase 2 (ADA2). The varying phenotypes of the disease often lead to delayed diagnosis or misdiagnosis. We report an 11-year-old boy with DADA2 and provide a preliminary analysis of genotype-phenotype correlation. The age of onset of the disease was 8 years old. The disease successively involved the brainstem, muscles, joints, and cerebrum. After three relapse-remission episodes over 3 years, the patient was finally diagnosed with DADA2 by whole-exome sequencing. Compound heterozygous variants in the ADA2 gene (NM_001282225.2: c.1072G>A, p.Gly358Arg; c.419dupC, p.Arg141Lysfs*37) were found in the patient. He did not receive anti-TNF therapy and had no relapse after a 8-month follow-up. We identified a novel variant of the ADA2 gene, and the associated disease course may follow a relapse-remission pattern. Homozygous mutations of p.Gly358Arg can cause pure red cell aplasia, whereas compound heterozygous variations may lead to different phenotypes. Variants in the catalytic domain and frameshift mutations may also cause relatively benign phenotypes besides causing hematological disorders. Further studies are needed to clarify the genotypic-phenotypic relationship of this disease.

The New Frontiers of Gene Therapy and Gene Editing in Inflammatory Diseases

Inflammatory diseases are conditions characterized by abnormal and often excessive immune responses, leading to tissue and organ inflammation. The complexity of these disorders arises from the intricate interplay of genetic factors and immune responses, which challenges conventional therapeutic approaches. However, the field of genetic manipulation has sparked unprecedented optimism in addressing these complex disorders. This review aims to comprehensively explore the application of gene therapy and gene editing in the context of inflammatory diseases, offering solutions that range from correcting genetic defects to precise immune modulation. These therapies have exhibited remarkable potential in ameliorating symptoms, improving quality of life, and even achieving disease remission. As we delve into recent breakthroughs and therapeutic applications, we illustrate how these advancements offer novel and transformative solutions for conditions that have traditionally eluded conventional treatments. By examining successful case studies and preclinical research, we emphasize the favorable results and substantial transformative impacts that gene-based interventions have demonstrated in patients and animal models of inflammatory diseases such as chronic granulomatous disease, cryopyrin-associated syndromes, and adenosine deaminase 2 deficiency, as well as those of multifactorial origins such as arthropathies (osteoarthritis, rheumatoid arthritis) and inflammatory bowel disease. In conclusion, gene therapy and gene editing offer transformative opportunities to address the underlying causes of inflammatory diseases, ushering in a new era of precision medicine and providing hope for personalized, targeted treatments.

Vasculitis and vasculopathy associated with inborn errors of immunity: an overview

Systemic autoinflammatory diseases (SAIDs) are disorders of innate immunity, which are characterized by unprovoked recurrent flares of systemic inflammation often characterized by fever associated with clinical manifestations mainly involving the musculoskeletal, mucocutaneous, gastrointestinal, and nervous systems. Several conditions also present with varied, sometimes prominent, involvement of the vascular system, with features of vasculitis characterized by variable target vessel involvement and organ damage. Here, we report a systematic review of vasculitis and vasculopathy associated with inborn errors of immunity.

Neurological phenotype of adenosine deaminase 2 deficient patients: a cohort study

BACKGROUND AND PURPOSE

Patients with adenosine deaminase 2 (ADA2) deficiency can present with various neurological manifestations due to vasculopathies and autoinflammation. These include ischaemic and hemorrhagic stroke, but less clearly defined neurological symptoms have also been reported.

METHODS

In this cohort study, patients with confirmed ADA2 deficiency from seven university hospitals in the Netherlands were included. The frequency and recurrence rates of neurological manifestations before and after initiation of tumor necrosis factor α (TNF-α) inhibiting therapy were analyzed.

RESULTS

Twenty-nine patients were included with a median age at presentation of 5 years (interquartile range 1-17). Neurological manifestations occurred in 19/29 (66%) patients and were the presenting symptom in 9/29 (31%) patients. Transient ischaemic attack (TIA)/ischaemic stroke occurred in 12/29 (41%) patients and was the presenting symptom in 8/29 (28%) patients. In total, 25 TIAs/ischaemic strokes occurred in 12 patients, one after initiation of TNF-α inhibiting therapy and one whilst switching between TNF-α inhibitors. None was large-vessel occlusion stroke. Two hemorrhagic strokes occurred: one aneurysmatic subarachnoid hemorrhage and one spontaneous intracerebral hemorrhage. Most neurological symptoms, including cranial nerve deficits, vertigo, ataxia and seizures, were caused by TIAs/ischaemic strokes and seldom recurred after initiation of TNF-α inhibiting therapy.

CONCLUSIONS

Neurological manifestations, especially TIA/ischaemic stroke, are common in patients with ADA2 deficiency and frequently are the presenting symptom. Because it is a treatable cause of young stroke, for which antiplatelet and anticoagulant therapy are considered contraindicated, awareness amongst neurologists and pediatricians is important. Screening for ADA2 deficiency in young patients with small-vessel ischaemic stroke without an identified cause should be considered.

Infliximab as successful treatment option in a case of adenosine deaminase 2 deficiency

Deficiency of adenosine deaminase 2 (DADA2) is a recessively inherited autoinflammatory disease characterized by systemic inflammation and immunodeficiency. Infliximab proved to be favorable in the treatment of this condition. This case report is concerned with a DADA2 deficient patient treated with infliximab. This is a rare case of DADA2 in a 32-year-old female patient. The patient was admitted with a clinical presentation of erythema, ulcers, and pruritus on both legs and ankles, accompanied by red ulcerative oral lesions, fatigue, malaise, and dizziness. The patient's genetic analysis was positive for DADA2. Treatment based on TNF-α inhibition was highly effective for this patient. We used laboratory testing and punch biopsy as differential diagnostic tools, where antinuclear antibody positivity, high prolactin levels, and high serum C-reactive protein were observed. The punch biopsy revealed both orthohyperkeratosis and parahyperkeratosis of the dermis, diffuse core fragments, plasma in the stratum corneum, and hypergranulous acanthosis. DADA2 treatment is centered on tumor necrosis factor α suppression. Although high-dose systemic glucocorticoids can reduce inflammation in the initial stages of the disease, most patients have a resistant or relapsing response to tapering attempts. The prevalence of undiagnosed cases of autoinflammatory diseases is anticipated to diminish with the growing awareness of them.

How to Build a Fire: The Genetics of Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAIDs) are a heterogeneous group of disorders caused by excess activation of the innate immune system in an antigen-independent manner. Starting with the discovery of the causal gene for familial Mediterranean fever, more than 50 monogenic SAIDs have been described. These discoveries, paired with advances in immunology and genomics, have allowed our understanding of these diseases to improve drastically in the last decade. The genetic causes of SAIDs are complex and include both germline and somatic pathogenic variants that affect various inflammatory signaling pathways. We provide an overview of the acquired SAIDs from a genetic perspective and summarize the clinical phenotypes and mechanism(s) of inflammation, aiming to provide a comprehensive understanding of the pathogenesis of autoinflammatory diseases.

Clinical Symptoms, Laboratory Parameters and Long-Term Follow-up in a National DADA2 Cohort

Deficiency of adenosine deaminase-2 (DADA2) is an autosomal recessive autoinflammatory disease with an extremely variable disease presentation. This paper provides a comprehensive overview of the Dutch DADA2 cohort. We performed a retrospective cohort study in 29 ADA2-deficient patients from 23 families with a median age at inclusion of 26 years. All patients had biallelic pathogenic variants in the ADA2 gene. The most common clinical findings included cutaneous involvement (79.3%), (hepato)splenomegaly (70.8%) and recurrent infections (58.6%). Stroke was observed in 41.4% of the patients. The main laboratory abnormalities were hypogammaglobulinemia and various cytopenias. Patients presented most often with a mixed phenotype involving vasculopathy, immunodeficiency and hematologic manifestations (62.1%). In this cohort, malignancies were reported in eight patients (27.6%), of whom five presented with a hematologic malignancy and two with a basal cell carcinoma. Four patients developed hemophagocytic lymphohistiocytosis (HLH) or an HLH-like episode, of whom three passed away during or shortly after the occurrence of HLH. TNF-inhibitors (TNFi) were effective in treating vasculopathy-associated symptoms and preventing stroke, but were hardly effective in the treatment of hematologic manifestations. Three patients underwent hematopoietic cell transplantation and two of them are doing well with complete resolution of DADA2-related symptoms. The overall mortality in this cohort was 17.2%. In conclusion, this cohort describes the clinical, genetic and laboratory findings of 29 Dutch DADA2 patients. We describe the occurrence of HLH as a life-threatening disease complication and report a relatively high incidence of malignancies and mortality.

Tailing growth, neonatal jaundice and anaemia

At medical school, there is a phrase to help us remember that common things are common: 'If you hear hooves think horses, not zebras'. However, zebras do exist, and from time to time in general paediatric and neonatal practice, we will encounter these rare diagnoses, more of which we can now accurately diagnose through the ever-expanding field of genomics. Our case demonstrates how a rare diagnosis can present with common features of growth restriction, jaundice and anaemia. Paediatricians therefore require a high index of suspicion and increasing knowledge of the logistics of genetic testing.

Brainstem Infarction in Immunodeficiency Identified as Adenosine Deaminase 2 Deficiency: Case Report

PURPOSE

We present the case of a 24-year-old male with CNS granulomatosis due to an immunodeficiency syndrome which was identified as deficiency of adenosine deaminase 2 (DADA2) as a cause of brainstem infarction.

METHODS

Case report and detailed description of the clinical course of diagnosis and treatment.

CASE

The patient's medical history consisted of an unknown immunodeficiency syndrome. Based on former findings, common variable immunodeficiency (CVID) was diagnosed. The patient suffered from three consecutive brainstem strokes of unknown etiology within 3 years. An MRI scan detected gadolinium-enhancing, granulomatous-suspect lesions in the interpeduncular cistern, temporal lobe, and tegmentum. Laboratory analysis was compatible with CVID, with leukopenia and immunoglobulin deficiency. Because granulomatous CNS inflammation was suspected, the patient received methylprednisolone immunosuppressive therapy, which led to partially regressive MRI lesions. However, in contrast to imaging, the patient showed a progressive cerebellar syndrome, indicating plasma exchange therapy and immunoglobulin treatment, which led to rapid symptom amelioration. After a relapse and a further stroke, expanded analysis confirmed DADA2 (and not CVID) as the inflammatory cause for recurrent stroke. After starting the therapy with immunoglobulins and adalimumab, no further strokes occurred.

CONCLUSION

We present the case of a young adult with diagnosis of DADA2 as a cause for recurrent strokes due to vasculitis. This stroke etiology is rare but should be considered as a cause of recurrent stroke of unknown origin in young patients to avoid a disabling disease course by disease-specific treatment options.

Comparison of disease phenotypes and mechanistic insight on causal variants in patients with DADA2

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) results in heterogeneous manifestations including systemic vasculitis and red cell aplasia. The basis of different disease phenotypes remains incompletely defined.

OBJECTIVE

We sought to further delineate disease phenotypes in DADA2 and define the mechanistic basis of ADA2 variants.

METHODS

We analyzed the clinical features and ADA2 variants in 33 patients with DADA2. We compared the transcriptomic profile of 14 patients by bulk RNA sequencing. ADA2 variants were expressed experimentally to determine impact on protein production, trafficking, release, and enzymatic function.

RESULTS

Transcriptomic analysis of PBMCs from DADA2 patients with the vasculitis phenotype or pure red cell aplasia phenotype exhibited similar upregulation of TNF, type I interferon, and type II interferon signaling pathways compared with healthy controls. These pathways were also activated in 3 asymptomatic individuals with DADA2. Analysis of ADA2 variants, including 7 novel variants, showed different mechanisms of functional disruption including (1) unstable transcript leading to RNA degradation; (2) impairment of ADA2 secretion because of retention in the endoplasmic reticulum; (3) normal expression and secretion of ADA2 that lacks enzymatic function; and (4) disruption of the N-terminal signal peptide leading to cytoplasmic localization of unglycosylated protein.

CONCLUSIONS

Transcriptomic signatures of inflammation are observed in patients with different disease phenotypes, including some asymptomatic individuals. Disease-associated ADA2 variants affect protein function by multiple mechanisms, which may contribute to the clinical heterogeneity of DADA2.

Interferonopathies masquerading as non-Mendelian autoimmune diseases: pattern recognition for early diagnosis

Type I interferonopathies are a broad category of conditions associated with increased type I interferon gene expression and include monogenic autoinflammatory diseases and non-Mendelian autoimmune diseases such as dermatomyositis and systemic lupus erythematosus. While a wide range of clinical presentations among type I interferonopathies exists, these conditions often share several clinical manifestations and implications for treatment. Presenting symptoms may mimic non-Mendelian autoimmune diseases, including vasculitis and systemic lupus erythematosus, leading to delayed or missed diagnosis. This review aims to raise awareness about the varied presentations of monogenic interferonopathies to provide early recognition and appropriate treatment to prevent irreversible damage and improve quality of life and outcomes in this unique patient population.

Deficiency of adenosine deaminase 2 as an unrecognized cause of early-onset stroke and cranial nerve palsy

OBJECTIVE

The aim of this study is to evaluate the clinical, laboratory, and radiological findings and prognosis of patients with adenosine deaminase 2 deficiency (DADA2) and to highlight the conditions that DADA2 should be considered in the differential diagnosis in patients with neurological findings.

METHODS

A case series of six DADA2 patients was presented in this retrospective, descriptive study. Clinical and laboratory data, treatment protocols, and prognosis of the patients were recorded. A diagnosis of DADA2 was established by ADA2 enzyme activity assay and/or ADA2 gene sequencing.

RESULTS

Six patients with DADA2 were included in the study. The median age at symptom onset was 6.5 years (range 3.5-13.5 years). The median time to diagnosis from the initial presentation was 9 (3-72) months. Consanguinity was present in the families of 4 cases. The skin, nervous system, and musculoskeletal system were the most commonly involved systems. Vasculitis mimicking polyarteritis nodosa (PAN) was the predominant phenotype (n=4) in our case series. Four patients with PAN-like features had neurological involvement. Ischemic strokes were found in 3 patients, cranial nerve palsy in 2 patients, and seizures in 2 patients. The CECR1 gene was analyzed in all patients. We analyzed plasma ADA2 enzyme activity only in one patient. Anti-tumor necrosis factor (TNF)-α therapy was initiated. Inflammation was suppressed and remission was achieved in all patients.

CONCLUSION

DADA2 should be considered in patients with PAN-like disease, a history of familial PAN/vasculitis, early-onset strokes/neurological involvement with systemic inflammation. Furthermore, anti-TNF-α therapy appears to be beneficial for the treatment of DADA2.

Inborn Errors of Immunity and Autoimmune Disease

Autoimmunity may be a manifestation of inborn errors of immunity, specifically as part of the subgroup of primary immunodeficiency known as primary immune regulatory disorders. However, although making a single gene diagnosis can have important implications for prognosis and management, picking patients to screen can be difficult, against a background of a high prevalence of autoimmune disease in the population. This review compares the genetics of common polygenic and rare monogenic autoimmunity, and explores the molecular mechanisms, phenotypes, and inheritance of autoimmunity associated with primary immune regulatory disorders, highlighting the emerging importance of gain-of-function and non-germline somatic mutations. A novel framework for identifying rare monogenic cases of common diseases in children is presented, highlighting important clinical and immunologic features that favor single gene disease and guides clinicians in selecting appropriate patients for genomic screening. In addition, there will be a review of autoimmunity in non-genetically defined primary immunodeficiency such as common variable immunodeficiency, and of instances where primary autoimmunity can result in clinical phenocopies of inborn errors of immunity.

A brazilian nationwide multicenter study on deficiency of deaminase-2 (DADA2)

INTRODUCTION

The deficiency of ADA2 (DADA2) is a rare autoinflammatory disease provoked by mutations in the ADA2 gene inherited in a recessive fashion. Up to this moment there is no consensus for the treatment of DADA2 and anti-TNF is the therapy of choice for chronic management whereas bone marrow transplantation is considered for refractory or severe phenotypes. Data from Brazil is scarce and this multicentric study reports 18 patients with DADA2 from Brazil.

PATIENTS AND METHODS

This is a multicentric study proposed by the Center for Rare and Immunological Disorders of the Hospital 9 de Julho - DASA, São Paulo - Brazil. Patients of any age with a confirmed diagnosis of DADA2 were eligible for this project and data on clinical, laboratory, genetics and treatment were collected.

RESULTS

Eighteen patients from 10 different centers are reported here. All patients had disease onset at the pediatric age (median of 5 years) and most of them from the state of São Paulo. Vasculopathy with recurrent stroke was the most common phenotype but atypical phenotypes compatible with ALPS-like and Common Variable Immunodeficiency (CVID) was also found. All patients carried pathogenic mutations in the ADA2 gene. Acute management of vasculitis was not satisfactory with steroids in many patients and all those who used anti-TNF had favorable responses.

CONCLUSION

The low number of patients diagnosed with DADA2 in Brazil reinforces the need for disease awareness for this condition. Moreover, the absence of guidelines for diagnosis and management is also necessary (t).

A wide spectrum of phenotype of deficiency of deaminase 2 (DADA2): a systematic literature review

INTRODUCTION

Deficiency of adenosine deaminase 2 (DADA2) is a rare monogenic autoinflammatory disease, whose clinical phenotype was expanded since the first cases, originally described as mimicker of polyarteritis nodosa, with immunodeficiency and early-onset stroke.

METHODS

A systematic review according to PRISMA approach, including all articles published before the 31st of August 2021 in Pubmed and EMBASE database was performed.

RESULTS

The search identified 90 publications describing 378 unique patients (55.8% male). To date 95unique mutations have been reported. The mean age at disease onset was 92.15 months (range 0-720 months), 32 (8.5%) showed an onset of the first signs/symptoms after 18 years old and 96 (25.4%) after 10 years old. The most frequent clinical characteristics described were cutaneous (67.9%), haematological manifestations (56.3%), recurrent fever (51.3%), neurological as stroke and polyneuropathy (51%), immunological abnormalities (42.3%), arthralgia/arthritis (35.4%), splenomegaly (30.6%), abdominal involvement (29.8%), hepatomegaly (23.5%), recurrent infections (18.5%), myalgia (17.9%), kidney involvement (17.7%) etc. Patients with skin manifestations were older than the others (101.1 months SD ± 116.5, vs. 75.3 SD ± 88.2, p 0.041), while those with a haematological involvement (64.1 months SD ± 75.6 vs. 133.1 SD ± 133.1, p < 0.001) and immunological involvement (73.03 months SD ± 96.9 vs. 103.2 SD ± 112.9, p 0.05) are younger than the others. We observed different correlations among the different clinical manifestations. The use of anti-TNFα and hematopoietic cell stems transplantation (HCST) has improved the current history of the disease.

CONCLUSION

Due to this highly variable phenotype and age of presentation, patients with DADA2 may present to several type of specialists. Given the important morbidity and mortality, early diagnosis and treatment are mandatory.

TNF-Blockade for Primary Stroke Prevention in Adenosine Deaminase 2 Deficiency: A Case Series

OBJECTIVES

Adenosine deaminase 2 deficiency (DADA2) is a genetic, neurologic, and systemic vasculitis syndrome, which can lead to recurrent strokes, typically lacunar. In the cohort of now 60 patients followed up at the NIH Clinical Center (NIH CC), no patient has had a stroke since starting tumor necrosis factor (TNF) blockade. We present a family with multiple affected children to highlight the importance of TNF blockade not just as secondary stroke prevention but also as primary stroke prevention in genetically affected but clinically asymptomatic patients.

METHODS

A proband with recurrent cryptogenic strokes was referred for evaluation at the NIH CC. The parents and 3 clinically asymptomatic siblings were also evaluated.

RESULTS

The proband was diagnosed with DADA2 based on biochemical testing; her antiplatelet therapies were discontinued, and she was started on TNF blockade for secondary stroke prevention. Her 3 asymptomatic siblings were subsequently tested and 2 were found to be biochemically affected. One of them elected to start TNF blockade for primary stroke prevention and the other sibling declined this approach and experienced a stroke. A second genetic sequence variant was subsequently identified in the ADA2 gene.

DISCUSSION

This family illustrates the importance of testing for DADA2 in young patients with cryptogenic stroke, given the hemorrhagic risks with antiplatelet drugs in these patients and effectiveness of TNF blockade as secondary stroke prevention. In addition, this family highlights the importance of screening all siblings of affected patients because they may be presymptomatic, and we advocate starting TNF blockade for primary stroke prevention in those who are found to be genetically or biochemically affected.

Ischaemic cerebral small vessel disease caused by adenosine deaminase 2 deficiency syndrome

BACKGROUND AND PURPOSE

Only a small proportion of cerebral small vessel disease (cSVD), a frequent cause of stroke and cognitive or motor disability in adults, is attributable to monogenic conditions. The hereditary nature of a patient's cSVD may be masked by a mild or non-informative phenotype, as single-gene disorders have a variable mode of presentation, penetrance and disease severity.

CASE DESCRIPTION

An adult patient is here described with recurrent acute ischaemic strokes due to cSVD with no other phenotypic manifestation, in whom the pathogenic c.139G>A (p.G47R) missense variant in ADA2 (NM_001282225.2), consistent with the diagnosis of adenosine deaminase 2 deficiency syndrome, was detected by targeted next-generation sequencing.

CONCLUSIONS

Clinical suspicion of adenosine deaminase 2 deficiency syndrome may be overlooked in stroke patients in whom other specific disease features are lacking. This case enlarges the mode of presentation of the syndrome and highlights the diagnostic potential of next-generation sequencing of known cSVD genes in young adults with recurrent small subcortical infarcts presenting with a lacunar syndrome.

Biologics and JAK inhibitors for the treatment of monogenic systemic autoinflammatory diseases in children

Systemic autoinflammatory diseases (SAIDs) are caused by aberrant activation of 1 or more inflammatory pathways in an antigen-independent manner. Monogenic forms of SAIDs typically manifest during childhood, and early treatment is essential to minimize morbidity and mortality. On the basis of the mechanism of disease and the dominant cytokine(s) that propagates inflammation, monogenic SAIDs can be grouped into major categories including inflammasomopathies/disorders of IL-1, interferonopathies, and disorders of nuclear factor-κB and/or aberrant TNF activity. This classification scheme has direct therapeutic relevance given the availability of biologic agents and small-molecule inhibitors that specifically target these pathways. Here, we review the experience of using biologics that target IL-1 and TNF as well as using Janus kinase inhibitors for the treatment of monogenic SAIDs in pediatric patients. We provide an evidence-based guide for the use of these medications and discuss their mechanism of action, safety profile, and strategies for therapeutic monitoring.

Deficiency of adenosine deaminase 2 (DADA2): Review

The deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease caused by loss-of-function (LOF) mutations in the ADA2 gene and was first described in 2014. Initially, it was described as vasculopathy/vasculitis that mostly affected infants and young children and closely resembled polyarteritis nodosa (PAN). Skin rash and ischemic/hemorrhagic stroke are predominant symptoms. However, the clinical spectrum of DADA2 has continued to expand since then. It has now been reported in adults as well. Besides vasculitis-related manifestations, hematological, immunological, and autoinflammatory manifestations are now well recognized. More than 100 disease-causing mutations have been described. The decrease in ADA2 enzyme leads to an increased extracellular adenosine level that, in turn, triggers a proinflammatory cascade. The disease is highly variable, and patients carrying same mutation may have different ages of presentation and clinical features. Anti-tumor necrosis factor (TNF) agents are mainstay of treatment of the vasculitis/vasculopathy phenotype. Hematopoietic stem cell transplant (HSCT) has been performed in patients with severe hematological manifestations. Recombinant ADA2 protein and gene therapy hold a promise for future.

Genotype and Phenotype of Adenosine Deaminase 2 Deficiency: a Report from Saudi Arabia

Adenosine deaminase 2 deficiency (DADA2), a rare and potentially fatal systemic autoinflammatory disease, is characterized by low or lack of ADA2 activity due to ADA2 mutations. DADA2 symptoms are variable and include vasculitis, immunodeficiency, and cytopenia. Minimal data are available from Saudi Arabia. This retrospective study conducted at seven major tertiary medical centers examined the phenotypic and genotypic variabilities, clinical and diagnostic findings, and treatment outcomes among 20 Saudi patients with DADA2 from 14 families. The median age of the study cohort was 9.5 years (4-26 years). The clinical presentation was before the age of 5 months in 25% of patients. Homozygous c.1447-1451del mutation was the most frequent ADA2 alteration (40%), followed by c.882-2A:G (30%). All tested patients exhibited absent or near-absent ADA2 activity. Phenotypic manifestations included stroke (40%), hematological abnormalities (95%), lymphoproliferation (65%), and recurrent infection (45%). Five and three patients had extracranial vasculitis features and Hodgkin lymphoma, respectively. Atypical manifestations included growth retardation (30%) and transverse myelitis. Anti-tumor necrosis factor (anti-TNF) therapy was the main treatment. Some patients underwent blood transfusion, splenectomy, cyclosporine and colony-stimulating factor therapies, and hematopoietic stem cell transplantation due to anti-TNF therapy failure. Fulminant hepatitis and septic multiorgan failure caused mortality in three patients. Thus, this study revealed the variability in the molecular and clinical characteristics of DADA2 in the study cohort with predominant aberrant hematological and immunological characteristics. Consensus diagnostic criteria will facilitate early diagnosis and treatment. Additionally, disease registries or large prospective studies are needed for evaluating rare disease complications, such as cancer.

ADA2 deficiency (DADA2) misdiagnosed as systemic onset juvenile idiopathic arthritis in a child carrying a novel compound heterozygous ADA2 mutation: a case report

BACKGROUND

The deficiency of adenosine deaminase 2 (DADA2) is caused by an autosomal recessive bi-allelic loss-of-function mutation in the adenosine deaminase 2 (ADA2) gene. DADA2 is a monogenic inherited autoinflammatory disorder characterized by early-onset vasculopathy for which the symptoms range from skin lesions to very severe multiorgan involvement, including life-threatening ischemia and/or hemorrhagic strokes. Owing to the diversity of clinical presentation and the absence of suggestive features, differentiating DADA2 from other inflammatory disorders in the early stages of disease presentation is difficult. Here, we describe the case of a 3-year-old boy who had been misdiagnosed for nearly 2 years before he was definitively diagnosed with DADA2.

CASE DESCRIPTION

A previously healthy 3-year-old boy was initially diagnosed with systemic onset juvenile idiopathic arthritis (soJIA) owing to recurrent unprovoked fever and elevated acute phase reactants. He developed intractable hypertension during treatment, which his doctor considered an adverse drug reaction. Monogenic inherited autoinflammatory disorders were not suspected until the patient developed intestinal perforation and ensuing recurrent abdominal pain that coincided with fever. Gene sequence analysis revealed a novel compound heterozygous mutation in ADA2. The ADA2 enzyme activity was almost completely lost in the patient.

CONCLUSIONS

The broad phenotypic spectrum of DADA2 makes early diagnosis challenging. DADA2 should be considered in case of early-onset vasculitis, which is the most common phenotype of DADA2. Early identification and treatment will result in significant improvement of the disease.

Case Report: Interindividual variability and possible role of heterozygous variants in a family with deficiency of adenosine deaminase 2: are all heterozygous born equals?

Deficiency of adenosine deaminase 2 (DADA2) is a rare systemic autoinflammatory disease, typically with autosomal recessive inheritance, usually caused by biallelic loss of function mutations in the ADA2 gene. The phenotypic spectrum is broad, generally including fever, early-onset vasculitis, stroke, and hematologic dysfunction. Heterozygous carriers may show related signs and symptoms, usually milder and at an older age. Here we describe the case of two relatives, the proband and his mother, bearing an ADA2 homozygous pathogenic variant, and a heterozygous son. The proband was a 17-year-old boy with intermittent fever, lymphadenopathies, and mild hypogammaglobulinemia. He also had sporadic episodes of aphthosis, livedo reticularis and abdominal pain. Hypogammaglobulinemia was documented when he was 10 years old, and symptoms appeared in his late adolescence. The mother demonstrated mild hypogammaglobulinemia, chronic pericarditis since she was 30 years old and two transient episodes of diplopia without lacunar lesions on MRI. ADA2 (NM_001282225.2) sequencing identified both mother and son as homozygous for the c.1358A>G, p.(Tyr453Cys) variant. ADA2 activity in the proband and the mother was 80-fold lower than in the controls. Clinical features in both patients improved on anti-tumor necrosis factor therapy. An older son was found to be heterozygous for the same mutation post-mortem. He died at the age of 12 years due to a clinical picture of fever, lymphadenitis, skin rash and hypogammaglobulinemia evolving toward fatal multiorgan failure. Biopsies of skin, lymph nodes, and bone marrow excluded lymphomas and vasculitis. Despite being suspected of symptomatic carrier, the contribution of an additional variant in compound heterozygosity, or further genetic could not be ruled out, due to poor quality of DNA samples available. In conclusion, this familiar case demonstrated the wide range of phenotypic variability in DADA2. The search for ADA2 mutations and the assessment of ADA2 activity should be considered also in patients with the association of hypogammaglobulinemia and inflammatory conditions, also with late presentation and in absence of vasculitis. Furthermore, the clinical picture of the deceased carrier suggests a possible contribution of heterozygous pathogenic variants to inflammation.

Use of biologics to treat relapsing and/or refractory polyarteritis nodosa: data from a European collaborative study

OBJECTIVES

To describe the effectiveness and safety of biologics for the treatment of relapsing and/or refractory polyarteritis nodosa (PAN).

METHODS

A retrospective European collaborative study was conducted in patients with PAN who received biologics for relapsing and/or refractory disease.

RESULTS

Forty-two patients with PAN received a total of 53 biologic courses, including TNF-α blockers in 15 cases, rituximab (RTX) in 18 cases, tocilizumab (TCZ) in 10 cases and other biologics in 10 cases. TNF-α blockers and TCZ were mainly used for refractory diseases whereas RTX was mainly initiated for relapsing disease. After a median follow-up of 29 (8-50) months, remission, partial response, treatment failure and treatment discontinuation due to severe adverse events occurred in, respectively, 40%, 13%, 40% and 7% of patients receiving TNF-α blockers, 50%, none, 30% and 20% of TCZ recipients, and 33%, 11%, 56% and none of the RTX recipients. No remission was noted in patients treated with other biologics. Severe adverse events were observed in 14 (28%) patients without significant differences between the three biologics, leading to early biologics discontinuation in only three cases.

CONCLUSION

These results suggest that TCZ may be effective in relapsing and/or refractory PAN. Our data warrant further study to confirm these findings.

A novel frameshift variant in the ADA2 gene of a patient with a neurological phenotype: a case report

BACKGROUND

Adenosine deaminase 2 (ADA2) deficiency is an inherited autoinflammatory syndrome caused by a defect in the ADA2 gene. Most common manifestations include peripheral vasculopathy, early-onset stroke, immunodeficiency, and haematological manifestations. Patients with pathogenic variants that are more detrimental to ADA2's enzymatic function (e.g. frameshift) have been reported to be prone to developing hematological phenotype. We report here the case of a 13-year-old Caucasian girl with a novel frameshift variant in the ADA2 gene and a clinical phenotype of early-onset stroke.

CASE PRESENTATION

The patient was admitted to hospital with complaints of weakness in her right arm, unilateral facial weakness and speech problems. Her initial laboratory workup was normal; however, magnetic resonance imaging of her brain confirmed acute/subacute ischaemic changes in the posterior limb of the left-sided internal capsule and in the apical part of the thalamus. She also had manifestations of immunodeficiency - recurrent skin infections and otitis, chronic Molluscum contagiosum infection in anamnesis and B cell deficiency with a low level of serum IgA. The patient's DNA was analysed and two pathogenic variants were identified in the ADA2 gene, confirming a diagnosis of adenosine deaminase 2 (ADA2) deficiency. While one of the variants (c.506G > A (p.Arg169Gln)) has been reported previously, the other one is a novel frameshift variant, namely, c.464del (p.Pro155Hisfs*29). The patient received stroke rehabilitation, which significantly improved her functional state. Tumour necrosis factor inhibitor and methotrexate treatment was commenced, and the patient has remained stable with no further ischaemic events.

CONCLUSIONS

Although rare, ADA2 deficiency should be considered in patients with early-onset stroke, especially with concomitant manifestations of inflammatory features or immunodeficiency. This case report extends the genotypic spectrum of ADA2 deficiency.

Case Report: Deficiency of Adenosine Deaminase 2 (DADA2) as a Cause of Brainstem Stroke in a 3-Year-Old Girl and the Importance of Early Fast-Track Genetic Diagnostics to Influence Therapy

Deficiency of adenosine deaminase 2 (DADA2) is a rare Mendelian, autoinflammatory multiorgan disease. We report the case of a 3.8-year-old female patient who was admitted with an acute brainstem stroke and was diagnosed with DADA2 by early initiation of exome sequencing. We recommend that DADA2 and a genetic workup should be taken into account, when evaluating strokes in children even if no other than neurological symptoms are evident.

Recent topics related to etiology and clinical manifestations of cutaneous arteritis

Cutaneous polyarteritis nodosa (cPAN) was first reported by Lindberg in 1931. It has been recognized as a skin-limited vasculitis whose cutaneous histopathological features are indistinguishable from those of PAN. Cutaneous arteritis (CA) was defined as a form of single-organ vasculitis in the revised Chapel Hill Classification and was recognized as the same disease as cPAN. It became known that deficiency of adenosine deaminase 2 (DADA2) cases were included in cases that had been diagnosed with CA. Because of their similarity and differences in the treatment methods, DADA2 should be considered in CA cases, especially if they are diagnosed or developed in early childhood. Cutaneous arteritis may be classified as an immune complex-mediated vasculitis. It was reported that the pathogenesis of anti-lysosomal-associated membrane protein-2 (LAMP-2) antibodies and anti-phosphatidylserine-prothrombin complex (PS/PT) antibodies as good parameters in CA. The main skin manifestations include livedo racemosa, subcutaneous nodules, and ulcers. Although CA is recognized to have a benign clinical course, it has become known that it is easy to relapse. The existence of skin ulcers upon diagnosis or sensory neuropathies was suggested to be a predictor of poor prognosis. Cutaneous arteritis with them may need to be treated with more intensive therapies.

Adenosine Deaminase 2 Deficiency Caused by Biallele Variants Including Splicing Variant: The First Case in Korea

Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by pathogenic variants of the ADA2 gene and has similar clinical features to polyarteritis nodosa (PAN). We, herein, report a case of DADA2 in Korea that was diagnosed in a patient with childhood-onset PAN. The patient had a truncal ataxia and facial palsy caused by thalamic infarction at 34 months of age. Livedo reticularis with Raynaud phenomenon and abdominal pain with fever were followed. Radiologic examination showed multiple infarctions in brain and kidney. She was diagnosed with PAN using skin biopsy and angiography. She had severe hemorrhagic strokes despite medical treatments. Her disease activity was controlled after adding a tumor necrosis factor-α inhibitor. Molecular analysis revealed compound heterozygous pathogenic variants of ADA2 gene. This is the first case of DADA2 in Korea. Genetic analysis for ADA2 gene should be considered in patients with childhood-onset PAN.

Case Report: Susceptibility to viral infections and secondary hemophagocytic lymphohistiocytosis responsive to intravenous immunoglobulin as primary manifestations of adenosine deaminase 2 deficiency

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, including systemic vasculitis, immunodeficiency, and cytopenia. We report a case of a 16-year-old girl affected by recurrent viral infections [including cytomegalovirus (CMV)-related hepatitis and measles vaccine virus-associated manifestations] and persistent inflammation, which occurred after Parvovirus infection and complicated by secondary hemophagocytic lymphohistiocytosis (HLH). HLH’s first episode presented at 6 years of age and was preceded by persistent fever and arthralgia with evidence of Parvovirus B19 infection. The episode responded to intravenous steroids but relapsed during steroids tapering. High-dose intravenous immunoglobulin (IVIG) helped manage her clinical symptoms and systemic inflammation. The frequency of IVIG administration and the dosage were progressively reduced. At the age of 9, she experienced varicella zoster virus (VZV) reactivation followed by the recurrence of the inflammatory phenotype complicated by HLH with neurological involvement. Again, high-dose steroids and monthly IVIG resulted in a quick response. Targeted next-generation sequencing (NGS) for autoinflammatory diseases and immunodeficiencies revealed the homozygous Leu183Pro ADA2 mutation, which was confirmed by Sanger analysis. ADA2 enzymatic test showed a complete loss of ADA2 activity. For about 3 years, IVIG alone was completely effective in preventing flares of inflammation and neurological manifestations. Anti-TNF treatment was started at the age of 13 for the appearance of recurrent genital ulcers, with a complete response. This case further expands the clinical spectrum of DADA2 and emphasizes the importance of extensive genetic testing in clinical phenotypes characterized by persistent unspecific inflammatory syndromes. The use of high doses of IVIG might represent a possible effective immune modulator, especially in combination with anti-TNF treatment.

Biologics for immunoglobulin A vasculitis: targeting vasculitis or comorbid disease?

In this study, we aimed to evaluate the clinical features and treatments, including the use of biological disease-modifying anti-rheumatic drugs (bDMARDs) in a large cohort of pediatric and adult immunoglobulin A vasculitis (IgAV). Since data on the use of bDMARDs in IgAV are very limited, we collated the reasons for use of bDMARDs during the disease course. Patients who were enrolled in the Hacettepe University Vasculitis Research Centre (HUVAC) registry were included. In this prospective database dating from 2014, there were 436 IgAV patients classified as IgAV according to Ankara 2008 and/or American College of Rheumatology 1990 criteria. 88 adults and 330 pediatric IgAV patients were included as the main study group. Concomitant spondyloarthritis (SpA) was observed only in adult patients (10% vs 0% in children, p < 0.001). IgAV relapse was more common in adults than in children (p: 0.017). Adult patients were mostly treated with corticosteroid (p < 0.001) and conventional synthetic disease-modifying anti-rheumatic drug treatment (< 0.001), while more than half of the pediatric patients were followed up without immunosuppressive treatment. Ten (11%) adult patients used biologics. Among them, two patients used rituximab due to IgAV disease activity, three used infliximab due to SpA, three used etanercept due to SpA (one patient had a pediatric onset enthesitis-related arthritis), and two used anakinra due to recurrent familial Mediterranean fever attacks. This is the first study evaluating the use of all bDMARDs for any reason in the IgAV cohorts in the literature. None of the pediatric patients used biologics. Our data suggest biologics are mainly used for comorbid inflammatory diseases over refractory vasculitis in adult IgAV.

Adenosine Deaminase 2 Deficiency (DADA2): A Crosstalk Between Innate and Adaptive Immunity

Deficiency of Adenosine deaminase 2 (DADA2) is a monogenic autoinflammatory disorder presenting with a broad spectrum of clinical manifestations, including immunodeficiency, vasculopathy and hematologic disease. Biallelic mutations in ADA2 gene have been associated with a decreased ADA2 activity, leading to reduction in deamination of adenosine and deoxyadenosine into inosine and deoxyinosine and subsequent accumulation of extracellular adenosine. In the early reports, the pivotal role of innate immunity in DADA2 pathogenic mechanism has been underlined, showing a skewed polarization from the M2 macrophage subtype to the proinflammatory M1 subtype, with an increased production of inflammatory cytokines such as TNF-α. Subsequently, a dysregulation of NETosis, triggered by the excess of extracellular Adenosine, has been implicated in the pathogenesis of DADA2. In the last few years, evidence is piling up that adaptive immunity is profoundly altered in DADA2 patients, encompassing both T and B branches, with a disrupted homeostasis in T-cell subsets and a B-cell skewing defect. Type I/type II IFN pathway upregulation has been proposed as a possible core signature in DADA2 T cells and monocytes but also an increased IFN-β secretion directly from endothelial cells has been described. So far, a unifying clear pathophysiological explanation for the coexistence of systemic inflammation, immunedysregulation and hematological defects is lacking. In this review, we will explore thoroughly the latest understanding regarding DADA2 pathophysiological process, with a particular focus on dysregulation of both innate and adaptive immunity and their interacting role in the development of the disease.

Allogeneic Hematopoietic Cell Transplantation for Patients With Deficiency of Adenosine Deaminase 2 (DADA2): Approaches, Obstacles and Special Considerations

Deficiency of adenosine deaminase 2 (DADA2) is an inherited autosomal recessive disease characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages, end organ vasculitis), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure. Allogeneic hematopoietic cell transplantation (HCT) is curative for DADA2 as it reverses the hematological, immune and vascular phenotype of DADA2. The primary goal of HCT in DADA2, like in other non-malignant diseases, is engraftment with the establishment of normal hematopoiesis and normal immune function. Strategies in selecting a preparative regimen should take into consideration the specific vulnerabilities to endothelial dysfunction and liver toxicity in DADA2 patients. Overcoming an increased risk of graft rejection while minimizing organ toxicity, graft-versus-host disease, and infections can be particularly challenging in DADA2 patients. This review will discuss approaches to HCT in DADA2 patients including disease-specific considerations, barriers to successful engraftment, post-HCT complications, and clinical outcomes of published patients with DADA2 who have undergone HCT to date.

Polyarteritis nodosa: an evolving primary systemic vasculitis

Polyarteritis nodosa (PAN) is a primary form of vasculitis characterized by inflammation of primarily medium-sized arteries. Several key events have shaped the current spectrum of the disease including the separation of a subgroup with microscopic polyangiitis, the discovery of the association of hepatitis B, and the discovery of adenosine deaminase 2 deficiency (DADA2). With the discovery of secondary causes of PAN and changing nomenclature, the incidence of PAN has declined over time. Common manifestations include constitutional symptoms, skin involvement, peripheral neuropathy, gastrointestinal disease, and renal involvement. DADA2 is a genetic cause of medium vessel vasculitis that is important to distinguish from primary PAN as treatment with TNF inhibitors can prevent morbidity and mortality in those with a vasculitis phenotype. Treatment of systemic primary PAN involves the use of systemic immunosuppressive therapy largely guided by the severity of disease. With current treatment regimens, the prognosis has changed from a once uniformly fatal disease to a 5-year survival rate above 80%.

The Interactions Between Autoinflammation and Type 2 Immunity: From Mechanistic Studies to Epidemiologic Associations

Autoinflammatory diseases are a group of clinical syndromes characterized by constitutive overactivation of innate immune pathways. This results in increased production of or responses to monocyte- and neutrophil-derived cytokines such as interleukin-1β (IL-1β), Tumor Necrosis Factor-α (TNF-α), and Type 1 interferon (IFN). By contrast, clinical allergy is caused by dysregulated type 2 immunity, which is characterized by expansion of T helper 2 (Th2) cells and eosinophils, as well as overproduction of the associated cytokines IL-4, IL-5, IL-9, and IL-13. Traditionally, type 2 immune cells and autoinflammatory effectors were thought to counter-regulate each other. However, an expanding body of evidence suggests that, in some contexts, autoinflammatory pathways and cytokines may potentiate type 2 immune responses. Conversely, type 2 immune cells and cytokines can regulate autoinflammatory responses in complex and context-dependent manners. Here, we introduce the concepts of autoinflammation and type 2 immunity. We proceed to review the mechanisms by which autoinflammatory and type 2 immune responses can modulate each other. Finally, we discuss the epidemiology of type 2 immunity and clinical allergy in several monogenic and complex autoinflammatory diseases. In the future, these interactions between type 2 immunity and autoinflammation may help to expand the spectrum of autoinflammation and to guide the management of patients with various autoinflammatory and allergic diseases.

Lentiviral Mediated ADA2 Gene Transfer Corrects the Defects Associated With Deficiency of Adenosine Deaminase Type 2

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.

Polyarteritis nodosa

PURPOSE OF REVIEW

The aim is to review recent reports on childhood polyarteritis nodosa, including recent reports on treatment and outcome. Recently deficiency of adenosine deaminase-2 (ADA2), which may present as a polyarteritis nodosa-mimic, is becoming an important part of our practice. We also aim to highlight differences of childhood polyarteritis nodosa with deficiency of ADA2 as well as adult-onset disease.

RECENT FINDINGS

The few recent childhood series confirm the systemic nature of this vasculitis with predominantly medium-vessel involvement. American College of Rheumatology Vasculitis foundation has suggested recommendations for the management of this vasculitis. Unfortunately, we lack large patient numbers to provide us high evidence for the treatment of these patients. However, for induction mycophenolate mofetil or shorter courses of cyclophosphamide can be considered.Deficiency of ADA2 is now in the differential diagnosis of polyarteritis nodosa patients presenting with a family history and/or stroke with hematological and/or immunological abnormalities.

SUMMARY

We need collaborative work to define management and treatment strategies for childhood polyarteritis nodosa. Distinguishing deficiency of ADA2 is important because the treatment is different.

Atypical presentation of adenosine deaminase 2 deficiency with bi‐allelic ADA2 mutation

Herein, we report a case of VAIHS with atypical clinical presentation of perianal abscess, fistula fever, and bi‐cytopenia including pathogenic ADA2 mutation suggesting that ADA2 deficiency be considered as a differential diagnosis of enlarging cutaneous abscess with no evidence of wound healing in the setting of leukopenia and neutropenia.

Importance of the determination of enzymatic activity in the diagnosis of deficiency of adenosine deaminase 2 (DADA2)

OBJECTIVE

To describe the usefulness of determining the enzymatic activity of adenosine deaminase 2 (ADA2) in patients with suspected ADA2 deficiency (DADA2).

METHOD

Retrospective multicenter study. Review with analysis of the clinical, biochemical and genetic data of the patients in whom the enzymatic activity of ADA2 has been determined by spectrophotometric method.

RESULT

In 3 of the 20 patients, the diagnosis of DADA2 was confirmed by the combination of reduced enzyme activity and biallelic pathogenic variants in the CECR1 gene. In 2 patients with variants of uncertain significance in CECR1, the study of enzymatic activity allowed to rule out the disease.

CONCLUSIONS

The reduced enzymatic detection of ADA2 confirms the diagnosis of DADA2, particularly important in carriers of variants of uncertain significance in CECR1.

Mechanisms of vascular inflammation in deficiency of adenosine deaminase 2 (DADA2)

Deficiency of adenosine deaminase 2 (DADA2) was first described as a monogenic form of systemic vasculitis that closely resembles polyarteritis nodosa (PAN). The phenotypic spectrum of DADA2 has vastly expanded in recent years and now includes pure red cell aplasia, bone marrow failure syndrome, lymphoproliferative disease, and humoral immunodeficiency. Vasculitis remains the most common presentation of DADA2, and treatment with tumor necrosis factor inhibitors (TNFi) has shown remarkable efficacy in preventing stroke and ameliorating features of systemic inflammation. The precise function of ADA2 has not been elucidated, and how absence of ADA2 ignites inflammation is an active area of research. In this review, we will discuss the current understanding of DADA2 from research and clinical perspectives. We will evaluate several proposed functions of ADA2, including polarization of monocyte phenotype, regulation of neutrophil extracellular trap formation, and modulation of innate immunity. We will also review the role of inflammatory cytokines including TNF and type I interferons. Lastly, we will provide future perspectives on understanding the phenotypic heterogeneity of DADA2 and discuss potential treatment options.

The Spectrum of the Deficiency of Adenosine Deaminase 2: An Observational Analysis of a 60 Patient Cohort

The deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessively inherited disease that has undergone extensive phenotypic expansion since being first described in patients with fevers, recurrent strokes, livedo racemosa, and polyarteritis nodosa in 2014. It is now recognized that patients may develop multisystem disease that spans multiple medical subspecialties. Here, we describe the findings from a large single center longitudinal cohort of 60 patients, the broad phenotypic presentation, as well as highlight the cohort’s experience with hematopoietic cell transplantation and COVID-19. Disease manifestations could be separated into three major phenotypes: inflammatory/vascular, immune dysregulatory, and hematologic, however, most patients presented with significant overlap between these three phenotype groups. The cardinal features of the inflammatory/vascular group included cutaneous manifestations and stroke. Evidence of immune dysregulation was commonly observed, including hypogammaglobulinemia, absent to low class-switched memory B cells, and inadequate response to vaccination. Despite these findings, infectious complications were exceedingly rare in this cohort. Hematologic findings including pure red cell aplasia (PRCA), immune-mediated neutropenia, and pancytopenia were observed in half of patients. We significantly extended our experience using anti-TNF agents, with no strokes observed in 2026 patient months on TNF inhibitors. Meanwhile, hematologic and immune features had a more varied response to anti-TNF therapy. Six patients received a total of 10 allogeneic hematopoietic cell transplant (HCT) procedures, with secondary graft failure necessitating repeat HCTs in three patients, as well as unplanned donor cell infusions to avoid graft rejection. All transplanted patients had been on anti-TNF agents prior to HCT and received varying degrees of reduced-intensity or non-myeloablative conditioning. All transplanted patients are still alive and have discontinued anti-TNF therapy. The long-term follow up afforded by this large single-center study underscores the clinical heterogeneity of DADA2 and the potential for phenotypes to evolve in any individual patient.

Anti-TNF therapy for inflammatory bowel disease in patients with neurodegenerative Niemann-Pick disease Type C

Background:  Blockade of tumour necrosis factor (anti-TNF) is effective in patients with Crohn’s Disease but has been associated with infection risk and neurological complications such as demyelination. Niemann-Pick disease Type C1 (NPC1) is a lysosomal storage disorder presenting in childhood with neurological deterioration, liver damage and respiratory infections. Some NPC1 patients develop severe Crohn’s disease. Our objective was to investigate the safety and effectiveness of anti-TNF in NPC1 patients with Crohn’s disease. Methods: Retrospective data on phenotype and therapy response were collected in 2019-2020 for the time period 2014 to 2020 from patients in the UK, France, Germany and Canada with genetically confirmed NPC1 defects and intestinal inflammation. We investigated TNF secretion in peripheral blood mononuclear cells treated with NPC1 inhibitor in response to bacterial stimuli. Results: NPC1 inhibitor treated peripheral blood mononuclear cells (PBMCs) show significantly increased TNF production after lipopolysaccharide or bacterial challenge providing a rationale for anti-TNF therapy. We identified 4 NPC1 patients with Crohn’s disease (CD)-like intestinal inflammation treated using anti-TNF therapy (mean age of onset 8.1 years, mean treatment length 27.75 months, overall treatment period 9.25 patient years). Anti-TNF therapy was associated with reduced gastrointestinal symptoms with no apparent adverse neurological events. Therapy improved intestinal inflammation in 4 patients. Conclusions: Anti-TNF therapy appears safe in patients with NPC1 and is an effective treatment strategy for the management of intestinal inflammation in these patients.

Hereditary Systemic Autoinflammatory Diseases: Therapeutic Stratification

Hereditary systemic autoinflammatory diseases (SAIDs) are rare, often severe conditions characterised by mutations in the key regulators of innate immune responses. Dramatic advances in the molecular genetics and next-generation sequencing in the past decade enabled identification of novel mutations that play a pivotal role in the mechanistic pathways of inflammation. Although genetic testing may not always provide straightforward guidance in diagnosis and clinical decision making, through translational research, it sheds light into molecular immunopathogenesis, particularly in IL-1 inflammasome and cytokine signalling pathways. These remarkable insights provided a better understanding of autoinflammatory conditions and their association with the innate and adaptive immune systems, as well as leading to development of cytokine-targetted biologic treatments. Use of targetted therapeutics not only helps control disease flares, reduce acute-phase responses and prevent devastating complications such as amyloidosis, but also improves health-related quality of lives and support patients to pursue almost a normal life. Herein, we discuss the commonest monogenic SAIDs, describe their immunopathology, and summarise the approaches in the management and targetted treatment of these conditions, including presentation of novel data based on a cohort of children with these rare diseases from a single quaternary referral centre in London.

The Growing Spectrum of DADA2 Manifestations-Diagnostic and Therapeutic Challenges Revisited

Deficiency of Adenosine Deaminase Type 2 (DADA2) is a rare autosomal recessive inherited disorder with a variable phenotype including generalized or cerebral vasculitis and bone marrow failure. It is caused by variations in the adenosine deaminase 2 gene (ADA2), which leads to decreased adenosine deaminase 2 enzyme activity. Here we present three instructive scenarios that demonstrate DADA2 spectrum characteristics and provide a clear and thorough diagnostic and therapeutic workflow for effective patient care. Patient 1 illustrates cerebral vasculitis in DADA2. Genetic analysis reveals a compound heterozygosity including the novel ADA2 variant, p.V325Tfs^*7. In patient 2, different vasculitis phenotypes of the DADA2 spectrum are presented, all resulting from the homozygous ADA2 mutation p.Y453C. In this family, the potential risk for siblings is particularly evident. Patient 3 represents pure red cell aplasia with bone marrow failure in DADA2. Here, ultimately, stem cell transplantation is considered the curative treatment option. The diversity of the DADA2 spectrum often delays diagnosis and treatment of this vulnerable patient cohort. We therefore recommend early ADA2 enzyme activity measurement as a screening tool for patients and siblings at risk, and we expect early steroid-based remission induction will help avoid fatal outcomes.

Polyarteritis Nodosa: State of the art

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis that preferentially affects medium-sized vessels. The idiopathic form has become rare. Its treatment relies on corticosteroid therapy and is combined with cyclophosphamide infusions for severe forms. Secondary PANs were mainly associated with hepatitis B virus infection; they were treated with plasma exchange and antivirals in combination with short-term corticosteroid therapy. Other secondary forms of PAN are now becoming more common, such as those due to blood disorders. More recently, a monogenic form linked to adenosine deaminase-2 mutations has been identified. It requires treatment with TNF inhibitors to decrease the occurrence of ischemic central nervous system complications, which make it serious. Once remission is obtained, relapses are typically rare during PAN and affect 28% of idiopathic PANs, within an average of 26 months from the diagnosis. The prognosis has improved considerably, with 5- and 10-year survival rates of 83% and 74%.