Sequence-Based Screening of Patients With Idiopathic Polyarteritis Nodosa, Granulomatosis With Polyangiitis, and Microscopic Polyangiitis for Deleterious Genetic Variants in ADA2

Clinical Characteristics and Outcomes of Polyarteritis Nodosa: An International Study

OBJECTIVE

We describe the demographics, clinical features, disease course, and survival of polyarteritis nodosa (PAN) through an international collaboration (GLOBAL-PAN).

METHODS

Patients with PAN were recruited between 1990 and 2020 from observational cohorts of nine countries across Europe, Japan, and North America. Eligibility was retrospectively defined using the European Medicines Agency classification algorithm. Patients with PAN related to hepatitis B virus (n = 12) and two monogenic diseases mimicking PAN, deficiency of adenosine deaminase 2 enzyme (n = 16) or familial Mediterranean fever (n = 11), were excluded. Data regarding organ involvement, relapse, disease-related damage, and survival were analyzed.

RESULTS

Three hundred fifty-eight patients (female:male ratio 174:184), including those with systemic PAN (sPAN, n = 282) and cutaneous PAN (n = 76), were included. Twenty-five were pediatric onset. Mean ± SD age at diagnosis was 44.3 ± 18.1 years. Constitutional symptoms (71.5%), cutaneous involvement (70.5%), musculoskeletal findings (69.1%), and neurologic features (48.0%) were common manifestations. Among patients with sPAN, gastrointestinal involvement and proteinuria over 400 mg/day were reported in 52.2% and 11.2%, respectively. During a median (interquartile range) 59.6 (99.5) months of follow-up, relapse occurred in 48.5% of patients. One, 5- and 10-year survival rates for sPAN were 97.1%, 94.0%, and 89.0%, respectively. Predictors of death for sPAN included age ≥65 years at diagnosis, serum creatinine at diagnosis >140 μmol/L, gastrointestinal manifestations, and central nervous system (CNS) involvement.

CONCLUSION

The spectrum of PAN remains a complex, multifaceted disease. Relapse is common. Age ≥65 years and serum creatinine >140 μmol/L at diagnosis, as well as gastrointestinal and CNS involvement, are independent predictors of death in sPAN.

Inborn errors of immunity: A field without frontiers

The study of primary immunodeficiencies or inborn errors of immunity continues to drive our knowledge of the function of the human immune system. From the outset, the study of inborn errors has focused on unraveling genetic etiologies and molecular mechanisms. Aided by the continuous growth in genetic diagnostics, the field has moved from the study of an infection dominated phenotype to embrace and unravel diverse manifestations of autoinflammation, autoimmunity, malignancy, and severe allergy in all medical disciplines. It has now moved from the study of ultrarare presentations to producing meaningful impact in conditions as diverse as inflammatory bowel disease, neurological conditions, and hematology. Beyond offering immunogenetic diagnosis, the study of underlying inborn errors of immunity in these conditions points to targeted treatment which can be lifesaving.

Polyarteritis Nodosa: Old Disease, New Etiologies

Polyarteritis nodosa (PAN), also known as panarteritis nodosa, represents a form of necrotizing vasculitis that predominantly affects medium-sized vessels, although it is not restricted to them and can also involve smaller vessels. The clinical presentation is heterogeneous and characterized by a significant number of patients exhibiting general symptoms, including asthenia, fever, and unintended weight loss. Although PAN can involve virtually any organ, it preferentially affects the skin, nervous system, and the gastrointestinal tract. Orchitis is a rare but specific manifestation of PAN. The absence of granulomas, glomerulonephritis, and anti-neutrophil cytoplasmic antibodies serves to distinguish PAN from other types of vasculitis. Major complications consist of hemorrhagic and thrombotic events occurring in mesenteric, cardiac, cerebral, and renal systems. Historically, PAN was frequently linked to hepatitis B virus (HBV) infection, but this association has dramatically changed in recent years due to declining HBV prevalence. Current epidemiological research often identifies a connection between PAN and genetic syndromes as well as neoplasia. This article provides a comprehensive review of PAN, specifically focusing on the progression of its clinical manifestations over time.

A Narrative Review of the Neurological Manifestations of Human Adenosine Deaminase 2 Deficiency

Deficiency of human adenosine deaminase type 2 (DADA2) is a complex systemic autoinflammatory disorder characterized by vasculopathy, immune dysregulation, and hematologic abnormalities. The most notable neurological manifestations of DADA2 are strokes that can manifest with various neurological symptoms and are potentially fatal. However, neurological presentations can be diverse. We here present a review of the neurological manifestations of DADA2 to increase clinical awareness of DADA2 as the underlying diagnosis. We reviewed all published cases of DADA2 from 1 January 2014 until 19 July 2022 found via PubMed. A total of 129 articles describing the clinical features of DADA2 were included in the analysis. Six hundred twenty-eight patients diagnosed with DADA2 were included in the review. 50.3% of patients had at least signs of one reported neurological event, which was the initial or sole manifestation in 5.7% and 0.6%, respectively. 77.5% of patients with neurological manifestations had at least signs of one cerebrovascular accident, with lacunar strokes being the most common and 35.9% of them having multiple stroke episodes. There is a remarkable predilection for the brain stem and deep gray matter, with 37.3% and 41.6% of ischemic strokes, respectively. Other neurological involvement included neuropathies, focal neurological deficits, ophthalmological findings, convulsions, and headaches. In summary, neurological manifestations affect a significant proportion of patients with DADA2, and the phenotype is broad. Neurological manifestations can be the first and single manifestation of DADA2. Therefore, stroke, encephalitis, posterior reversible encephalopathy syndrome, mononeuropathy and polyneuropathy, and Behçet's disease-like presentations should prompt the neurologist to exclude DADA2, especially but not only in childhood.

A Successful Infliximab Treatment of a Pediatric Case of Severe Polyarteritis Nodosa With a Cerebral Infarction and a Decreased Adenosine Deaminase 2 Activity

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis common in males over 50 years of age that causes various organ symptoms. In recent years, it has become important to distinguish deficiency of adenosine deaminase 2 (DADA2) from childhood-onset PAN. A 13-year-old girl was urgently transferred to our hospital with sudden weakness in her right upper and lower limbs. The National Institutes of Health Stroke Scale (NIHSS) was 8. Plain MRI of the brain indicated high-signal areas in the right caudate nucleus, internal capsule, and left basal ganglia when applying T2-weighted, fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI); and low signals in the same regions in an apparent diffusion coefficient (ADC) map. It demonstrated inflammatory demyelinating disease of the central nervous system or multiple cerebral infarctions attributable to vasculitis, and it is difficult to differentiate between them based on image findings alone, and cannot be determined without following the clinical course. Hence, we treated with steroid therapy, which is effective for both conditions. Although the paralysis was alleviated, an MRI of the brain reperformed on day 7 revealed expansion of the lesion with contrast enhancement in the feeding area of the left lateral striatal artery, a high signal in DWI, and a low signal in an ADC map. Based on the clinical and radiological findings, we diagnosed a cerebral infarction attributable to vasculitis. Contrast computed tomography (CT) of her chest and abdominal CT angiography revealed that she met the diagnostic criteria for PAN, and adenosine deaminase 2 (AD2) activity level was low. The patient was treated with steroids combined with azathioprine and cyclophosphamide but three weeks after discharge developed a new cerebral infarction in the right basal ganglia. We commenced infliximab; no recurrence of cerebral infarction has been noted. The low AD2 activity may explain the intractable atypical course of this case. Further studies are needed to reveal the role of AD2 in patients with residual enzyme activity and reevaluation of the PAN diagnostic criteria is essential.

Clinical features and long-term outcomes of patients with systemic polyarteritis nodosa diagnosed since 2005: Data from 196 patients

BACKGROUND

The landscape of polyarteritis nodosa (PAN) has substantially changed during the last decades. Recent data regarding causes, characteristics, and prognosis of systemic PAN in the modern era are lacking.

METHODS

This retrospective study included patients with systemic PAN referred to the French Vasculitis Study Group between 2005 and 2019. Characteristics, associated conditions and outcomes were collected, and predictors of relapse and death were analyzed.

RESULTS

196 patients were included. Main clinical symptoms were constitutional (84%), neurological (59%), skin (58%) and musculoskeletal (58%) manifestations. Secondary PAN accounted for 55 (28%) patients, including myelodysplastic syndrome (9%), solid cancer (7%), lymphoma (4%) and autoinflammatory diseases (4%). No patient had active HBV infection. All treated patients (98.5%) received glucocorticoids (GCs), alone (41%) or in combination with immunosuppressants (59%), with remission achieved in 90%. Relapses were independently associated with age >65 years (HR 1.85; 95% CI1.12-3.08), gastrointestinal involvement (1.95; 95% CI1.09-3.52) and skin necrotic lesions (HR 1.95; 95%CI 1.24-3.05). One-, 5- and 10-year overall survival rates were 93%, 87% and 81%, respectively. In multivariate analyses, age >65 years (HR 2.80; 95%CI 1.23-6.37), necrotic purpura (HR 4.16; 95%CI 1.62-10.70), acute kidney injury (HR 4.89; 95% 1.71-13.99) and secondary PAN (HR 2.98; 95%CI 1.29-6.85) were independently associated with mortality.

CONCLUSION

Landscape of PAN has changed during the last decades, with the disappearance of HBV-PAN and the emergence of secondary PAN. Relapse rate remains high, especially in aged patients with gastrointestinal and cutaneous necrosis, as well as mortality.

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.

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.

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.

Vaskulitis mimics

Idiopathische Vaskulitiden sind seltene entzündliche Systemerkrankungen, die nach der Chapel-Hill Konsensus-Nomenklatur nach der Größe der prädominant betroffenen Gebiete von Blutgefäßen (große, mittelgroße, kleine Gefäße und Gefäße variabler Größe) eingeteilt werden. Vaskulitis mimics sind Syndrome, die ein ähnliches klinisches Bild hervorrufen oder leicht mit einer idiopathischen Vaskulitis verwechselt werden und teils sogar ein Krankheitsbild, das klinisch und histologisch einer Vaskulitis gleicht, auslösen können. Die Zahl der Vaskulitis mimics ist groß, je nach betroffenem Gefäßgebiet kommen hereditäre Erkrankungen des Bindegewebes, genetisch bedingte Immundefekt- und Autoinflammationssyndrome, infektiöse Erkrankungen, seltene entzündliche Systemerkrankungen, Tumorerkrankungen, medikamenteninduzierte Syndrome und zahlreiche weitere infrage. In diesem Review wird eine Auswahl klassischer Imitatoren von Vaskulitiden, orientiert an der Größe der betroffenen Blutgefäße präsentiert und Konstellationen, die typische „Fallstricke“ in der klinischen Abklärung darstellen können, diskutiert.

Immune dysregulation

The understanding of immune dysregulation in many different diseases continues to grow. There is increasing evidence that altered microbiome and gut barrier dysfunction contribute to systemic inflammation in patients with primary immunodeficiency and in patients with rheumatic disease. Recent research provides insight into the process of induction and maturation of pathogenic age-associated B cells and highlights the role of age-associated B cells in creating tissue inflammation. T follicular regulatory cells are shown to help maintain B-cell tolerance, and therapeutic approaches to increase or promote T follicular regulatory cells may help prevent or decrease immune dysregulation. Meanwhile, novel studies of systemic-onset juvenile idiopathic arthritis reveal a strong HLA association with interstitial lung disease and identify key aspects of the pathogenesis of macrophage activation syndrome. Studies of hyperinflammatory syndromes, including the recently described multisystem inflammatory syndrome of children, characterize similarities and differences in cytokine profiles and T-cell activation. This review focuses on recent advances in the understanding of immune dysregulation and describes potential key factors that may function as biomarkers for disease or targets for therapeutic interventions. Future trials are necessary to address the many remaining questions with regards to pathogenesis, diagnosis, and treatment of autoimmune, inflammatory, and immunodeficiency syndromes.

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.

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.

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.

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%.

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.

[Primary vasculitides in childhood and adulthood]

Primary systemic vasculitides can be observed at any age. Some vasculitides occur preferentially in childhood, such as Kawasaki syndrome or immunoglobulin A (IgA) vasculitis, whereas others, such as giant cell arteritis, occur beyond the age of 50 years. Vasculitides occurring in childhood or adolescence and adulthood may have different phenotypes, different disease courses and outcomes depending on the age of manifestation. For example, those with Takayasu arteritis beginning in adolescence have different vascular involvement, a higher degree of systemic inflammation and a more aggressive course of disease than those with adult-onset disease. In contrast, IgA vasculitis is more severe in adults than in children. The causes for the age predilections and different age-dependent disease manifestations have not yet been clarified. The therapeutic principles are similar for vasculitides occurring in children or adolescents and adults. The first international evidence-based treatment recommendations are now available for juvenile vasculitides, although the evidence for certain forms of treatment is still very limited. The treatment of adult vasculitides can be guided by numerous national and international guidelines and recommendations. Many vasculitides carry a high risk of morbidity and mortality and the timely detection and treatment are therefore necessary. In this article, similarities and differences in the clinical presentations, treatment, courses and prognosis of vasculitides in children or adolescents and adults are discussed.

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%.

Monogenic Adult-Onset Inborn Errors of Immunity

Inborn errors of immunity (IEI) are a heterogenous group of disorders driven by genetic defects that functionally impact the development and/or function of the innate and/or adaptive immune system. The majority of these disorders are thought to have polygenic background. However, the use of next-generation sequencing in patients with IEI has led to an increasing identification of monogenic causes, unravelling the exact pathophysiology of the disease and allowing the development of more targeted treatments. Monogenic IEI are not only seen in a pediatric population but also in adulthood, either due to the lack of awareness preventing childhood diagnosis or due to a delayed onset where (epi)genetic or environmental factors can play a role. In this review, we discuss the mechanisms accounting for adult-onset presentations and provide an overview of monogenic causes associated with adult-onset IEI.

Intrinsic Defects in B Cell Development and Differentiation, T Cell Exhaustion and Altered Unconventional T Cell Generation Characterize Human Adenosine Deaminase Type 2 Deficiency

PURPOSE

Deficiency of adenosine deaminase type 2 (ADA2) (DADA2) is a rare inborn error of immunity caused by deleterious biallelic mutations in ADA2. Clinical manifestations are diverse, ranging from severe vasculopathy with lacunar strokes to immunodeficiency with viral infections, hypogammaglobulinemia and bone marrow failure. Limited data are available on the phenotype and function of leukocytes from DADA2 patients. The aim of this study was to perform in-depth immunophenotyping and functional analysis of the impact of DADA2 on human lymphocytes.

METHODS

In-depth immunophenotyping and functional analyses were performed on ten patients with confirmed DADA2 and compared to heterozygous carriers of pathogenic ADA2 mutations and normal healthy controls.

RESULTS

The median age of the patients was 10 years (mean 20.7 years, range 1-44 years). Four out of ten patients were on treatment with steroids and/or etanercept or other immunosuppressives. We confirmed a defect in terminal B cell differentiation in DADA2 and reveal a block in B cell development in the bone marrow at the pro-B to pre-B cell stage. We also show impaired differentiation of CD4⁺ and CD8⁺ memory T cells, accelerated exhaustion/senescence, and impaired survival and granzyme production by ADA2 deficient CD8⁺ T cells. Unconventional T cells (i.e. iNKT, MAIT, Vδ2⁺ γδT) were diminished whereas pro-inflammatory monocytes and CD56^bright immature NK cells were increased. Expression of the IFN-induced lectin SIGLEC1 was increased on all monocyte subsets in DADA2 patients compared to healthy donors. Interestingly, the phenotype and function of lymphocytes from healthy heterozygous carriers were often intermediate to that of healthy donors and ADA2-deficient patients.

CONCLUSION

Extended immunophenotyping in DADA2 patients shows a complex immunophenotype. Our findings provide insight into the cellular mechanisms underlying some of the complex and heterogenous clinical features of DADA2. More research is needed to design targeted therapy to prevent viral infections in these patients with excessive inflammation as the overarching phenotype.

A Novel LC-MS/MS-Based Method for the Diagnosis of ADA2 Deficiency from Dried Plasma Spot

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.

2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Polyarteritis Nodosa

OBJECTIVE

To provide evidence-based recommendations and expert guidance for the management of systemic polyarteritis nodosa (PAN).

METHODS

Twenty-one clinical questions regarding diagnostic testing, treatment, and management were developed in the population, intervention, comparator, and outcome (PICO) format for systemic, non-hepatitis B-related PAN. Systematic literature reviews were conducted for each PICO question. The Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the quality of evidence and formulate recommendations. Each recommendation required ≥70% consensus among the Voting Panel.

RESULTS

We present 16 recommendations and 1 ungraded position statement for PAN. Most recommendations were graded as conditional due to the paucity of evidence. These recommendations support early treatment of severe PAN with cyclophosphamide and glucocorticoids, limiting toxicity through minimizing long-term exposure to both treatments, and the use of imaging and tissue biopsy for disease diagnosis. These recommendations endorse minimizing risk to the patient by using established therapy at disease onset and identify new areas where adjunctive therapy may be warranted.

CONCLUSION

These recommendations provide guidance regarding diagnostic strategies, use of pharmacologic agents, and imaging for patients with PAN.

2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Polyarteritis Nodosa

OBJECTIVE

To provide evidence-based recommendations and expert guidance for the management of systemic polyarteritis nodosa (PAN).

METHODS

Twenty-one clinical questions regarding diagnostic testing, treatment, and management were developed in the population, intervention, comparator, and outcome (PICO) format for systemic, non-hepatitis B-related PAN. Systematic literature reviews were conducted for each PICO question. The Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the quality of evidence and formulate recommendations. Each recommendation required ≥70% consensus among the Voting Panel.

RESULTS

We present 16 recommendations and 1 ungraded position statement for PAN. Most recommendations were graded as conditional due to the paucity of evidence. These recommendations support early treatment of severe PAN with cyclophosphamide and glucocorticoids, limiting toxicity through minimizing long-term exposure to both treatments, and the use of imaging and tissue biopsy for disease diagnosis. These recommendations endorse minimizing risk to the patient by using established therapy at disease onset and identify new areas where adjunctive therapy may be warranted.

CONCLUSION

These recommendations provide guidance regarding diagnostic strategies, use of pharmacologic agents, and imaging for patients with PAN.

Plasma Adenosine Deaminase (ADA)-1 and -2 Demonstrate Robust Ontogeny Across the First Four Months of Human Life

Background

Human adenosine deaminases (ADAs) modulate the immune response: ADA1 via metabolizing adenosine, a purine metabolite that inhibits pro-inflammatory and Th1 cytokine production, and the multi-functional ADA2, by enhancing T-cell proliferation and monocyte differentiation. Newborns are relatively deficient in ADA1 resulting in elevated plasma adenosine concentrations and a Th2/anti-inflammatory bias compared to adults. Despite the growing recognition of the role of ADAs in immune regulation, little is known about the ontogeny of ADA concentrations.

Methods

In a subgroup of the EPIC002-study, clinical data and plasma samples were collected from 540 Gambian infants at four time-points: day of birth; first week of life; one month of age; and four months of age. Concentrations of total extracellular ADA, ADA1, and ADA2 were measured by chromogenic assay and evaluated in relation to clinical data. Plasma cytokines/chemokine were measured across the first week of life and correlated to ADA concentrations.

Results

ADA2 demonstrated a steady rise across the first months of life, while ADA1 concentration significantly decreased 0.79-fold across the first week then increased 1.4-fold by four months of life. Males demonstrated significantly higher concentrations of ADA2 (1.1-fold) than females at four months; newborns with early-term (37 to <39 weeks) and late-term (≥41 weeks) gestational age demonstrated significantly higher ADA1 at birth (1.1-fold), and those born to mothers with advanced maternal age (≥35 years) had lower plasma concentrations of ADA2 at one month (0.93-fold). Plasma ADA1 concentrations were positively correlated with plasma CXCL8 during the first week of life, while ADA2 concentrations correlated positively with TNFα, IFNγ and CXCL10, and negatively with IL-6 and CXCL8.

Conclusions

The ratio of plasma ADA2/ADA1 concentration increased during the first week of life, after which both ADA1 and ADA2 increased across the first four months of life suggesting a gradual development of Th1/Th2 balanced immunity. Furthermore, ADA1 and ADA2 were positively correlated with cytokines/chemokines during the first week of life. Overall, ADA isoforms demonstrate robust ontogeny in newborns and infants but further mechanistic studies are needed to clarify their roles in early life immune development and the correlations with sex, gestational age, and maternal age that were observed.

Expanding spectrum of DADA2: a review of phenotypes, genetics, pathogenesis and treatment

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic disease caused by biallelic mutations in ADA2 gene (previously CECR1). The aim of this review was to describe the clinical phenotypes, genetics, pathogenesis and treatment of DADA2. ADA2 is highly expressed on myeloid cells and deficiency leads to polarisation of macrophages to an M1 inflammatory type and activation of neutrophils. The pathogenesis of immunological and haematological manifestations is less clear. The spectrum of clinical presentations varies widely from asymptomatic individual to severe vasculitis, several autoinflammatory, immunological and haematological manifestations. Initially considered a childhood disease, the first presentation is now being reported well into adulthood. Vasculitis closely resembles polyarteritis nodosa. Livedoid reticularis/racemosa like skin rash and central nervous system involvement in the form of ischemic or haemorrhagic stroke are dominant manifestations. Immunological manifestations include hypogammaglobulinemia and recurrent infections. Lymphopenia is the most common haematological manifestation; pure red cell aplasia and bone marrow failure has been reported in severe cases. The disease is extremely heterogeneous with variable severity noted in patients with the same mutation and even within family members. Tumour necrosis factor inhibitors are currently the treatment of choice for vasculitic and inflammatory manifestations and also prevent strokes. Haematopoietic stem cell transplantation is a curative option for severe haematological manifestations like pure red cell aplasia, bone marrow failure and immunodeficiency. Further research is required to understand pathogenesis and all clinical aspects of this disease to enable early diagnosis and prompt treatment. Key Points • Deficiency of adenosine deaminase 2 (DADA2) is a monogenic disease caused by biallelic mutations in ADA2 gene. • The clinical features include vasculitis resembling polyarteritis nodosa, autoinflammation, haematological manifestations and immunodeficiency. • The severity varies widely from mild to fatal even in patients within a family and with the same mutation. • The treatment of choice for inflammatory and vasculitic disease is tumour necrosis factor α blockers. Bone marrow transplant may be considered for severe haematological disease.

Advances in cutaneous vasculitis research and clinical care

Vasculitis is characterized by inflammation and destruction of blood vessels, resulting in downstream ischemic tissue damage. Diagnosis of vasculitis is a careful exercise in clinical-pathologic correlation, depending upon the clinical manifestations, organs involved, the size of affected blood vessels, imaging, and laboratory findings. While some vasculitis subtypes may be confined to the skin, serious internal organ involvement or underlying disease states may also occur. Accordingly, the skin plays an important role in the diagnostic process and may be prognostically important in some cases, signifying more severe systemic disease. The skin also provides opportunities for tissue-based translational research, improving understanding of disease pathophysiology. Dermatologists, therefore, play a critical role in evaluating vasculitis and helping to advance vasculitis clinical care and research. Recent updates in vasculitis nomenclature and terminology, evidence-based diagnosis, pathogenesis, and investigations of targeted therapies are changing vasculitis research and leading to fundamental shifts in disease management. Treatment advances favoring evidence-based and targeted, rather than broadly immunosuppressive, therapies are in development, while a multicenter trial for skin-limited vasculitis is ongoing. Collaborative multidisciplinary research networks are key to current and future advances in vasculitis research. In this review, we describe recent developments in vasculitis clinical care and research, starting with a discussion of efforts to develop diagnostic and classification criteria, followed by updates on the evaluation and treatment of vasculitis.