Deficiency of Human Adenosine Deaminase Type 2 - A Diagnostic Conundrum for the Hematologist

Deficiency of Adenosine Deaminase 2

Adenosine deaminase 2 (ADA2) deficiency is an autosomal recessively inherited autoinflammatory disorder caused by loss-of-function mutations in the ADA2 gene. Although the pathogenesis involves the triggering of a proinflammatory cascade due to increased production of inflammatory cytokines such as tumor necrosis factor (TNF)-α and dysregulation of neutrophil extracellular trap formation resulting from an excess accumulation of extracellular adenosine, the pathogenetic mechanism still needs further clarification due to the broad clinical spectrum. In addition to the initially described vasculitis-related symptoms, hematological, immunological, and autoinflammatory symptoms are now well recognized. The diagnosis is made by demonstration of pathogenic variants of ADA2 with biallelic loss of function and identification of low plasma ADA2 catalytic activity. Currently, TNF-α inhibitors are the treatment of choice for controlling vasculitis manifestations and preventing strokes. However, in patients presenting with severe hematologic findings, TNF-α inhibitors are not the treatment of choice and hematopoietic stem cell transplantation has been shown to be successful in selected cases. Recombinant ADA2 protein and gene therapy are promising treatment modalities for the future. In conclusion, ADA2 deficiency has a broad phenotype and should be considered in the differential diagnosis of different clinical situations. In this review, we summarize the disease manifestations of ADA2 deficiency and available treatment options.

Deficiency of adenosine deaminase 2 leading to recurrent Hodgkin lymphoma: A case report

Deficiency of adenosine deaminase 2 is a rare monogenic multi-organ disease of children and less often adults resulting from mutations in the adenosine deaminase 2 gene. We present a case of a 35-year-old Palestinian male with adenosine deaminase 2 deficiency and maturity-onset diabetes of the young type 2. The patient initially presented with complaints of swelling in his neck and night sweats, leading to a diagnosis of Hodgkin lymphoma. Subsequent evaluation revealed a recurrence of Hodgkin lymphoma, along with symptoms of otitis media, upper respiratory tract infection, and a rash around the mouth. Genetic testing confirmed mutations in the adenosine deaminase 2 gene and glucokinase genes, confirming the diagnosis of deficiency of adenosine deaminase 2 and maturity-onset diabetes of the young type 2, respectively. The patient was treated with Intravenous immunoglobulin, antiviral drugs, and oral hypoglycemic drugs, showing improvement in symptoms and laboratory tests. This case highlights the importance of considering rare genetic disorders in patients with unusual or refractory clinical manifestations, and the need for a multidisciplinary approach in such cases.

ADA2 regulates inflammation and hematopoietic stem cell emergence via the A2bR pathway in zebrafish

Deficiency of adenosine deaminase 2 (DADA2) is an inborn error of immunity caused by loss-of-function mutations in the adenosine deaminase 2 (ADA2) gene. Clinical manifestations of DADA2 include vasculopathy and immuno-hematological abnormalities, culminating in bone marrow failure. A major gap exists in our knowledge of the regulatory functions of ADA2 during inflammation and hematopoiesis, mainly due to the absence of an ADA2 orthologue in rodents. Exploring these mechanisms is essential for understanding disease pathology and developing new treatments. Zebrafish possess two ADA2 orthologues, cecr1a and cecr1b, with the latter showing functional conservation with human ADA2. We establish a cecr1b-loss-of-function zebrafish model that recapitulates the immuno-hematological and vascular manifestations observed in humans. Loss of Cecr1b disrupts hematopoietic stem cell specification, resulting in defective hematopoiesis. This defect is caused by induced inflammation in the vascular endothelium. Blocking inflammation, pharmacological modulation of the A2r pathway, or the administration of the recombinant human ADA2 corrects these defects, providing insights into the mechanistic link between ADA2 deficiency, inflammation and immuno-hematological abnormalities. Our findings open up potential therapeutic avenues for DADA2 patients.

Chronic neutropenia in childhood: experience of a tertiary center

OBJECTIVE

To assess the prevalence of chronic neutropenia (CN) and the clinical profile of patients with CN aged up to 18 years, followed in the pediatric hematology, rheumatology, or immunology outpatient clinic of a tertiary medical center from May 1, 2018, to 30 April 2019.

METHODS

Retrospective observational study carried out by collecting data from the patient's medical charts. CN was defined as absolute neutrophil count (ANC) below 1.5 × 109/L lasting over three months. Autoimmune neutropenia (AIN) was defined by clinical criteria and an over twofold increase in ANC after glucocorticoid stimulation. AIN was considered secondary when associated with autoimmune or immunoregulatory disorders. Wilcoxon and Fisher's exact tests were used to compare variables; the significance level was 5 %.

RESULTS

A total of 1,039 patients were evaluated; 217 (20 %) presented CN. Twenty-one (2 %) had AIN, classified as primary in 57 % of the cases. The average age at the onset of symptoms was 38.6 months. During follow-up, patients had 4.2 infections on average; frequency was higher among patients with secondary AIN (p = 003). Isolated neutropenia occurred in 43 % of the patients with AIN. Neutropenia resolved in eight (38 %) of the 21 patients with AIN within 19.6 months on average. Eight patients with secondary AIN met the criteria for Inborn Errors of Immunity.

CONCLUSION

AIN prevalence was 2 %. Most cases were first evaluated by a pediatric immunologist or rheumatologist rather than a pediatric hematologist. This study highlights the need for a multidisciplinary approach involving a pediatric immunologist, rheumatologist, and hematologist.

Post-transplant Inflammatory Bowel Disease Associated with Donor-Derived TIM-3 Deficiency

Inflammatory bowel disease (IBD) occurring following allogeneic stem cell transplantation (aSCT) is a very rare condition. The underlying pathogenesis needs to be better defined. There is currently no systematic effort to exclude loss- or gain-of-function mutations in immune-related genes in stem cell donors. This is despite the fact that more than 100 inborn errors of immunity may cause or contribute to IBD. We have molecularly characterized a patient who developed fulminant inflammatory bowel disease following aSCT with stable 100% donor-derived hematopoiesis. A pathogenic c.A291G; p.I97M HAVCR2 mutation encoding the immune checkpoint protein TIM-3 was identified in the patient's blood-derived DNA, while being absent in DNA derived from the skin. TIM-3 expression was much decreased in the patient's serum, and in vitro-activated patient-derived T cells expressed reduced TIM-3 levels. In contrast, T cell-intrinsic CD25 expression and production of inflammatory cytokines were preserved. TIM-3 expression was barely detectable in the immune cells of the patient's intestinal mucosa, while being detected unambiguously in the inflamed and non-inflamed colon from unrelated individuals. In conclusion, we report the first case of acquired, "transplanted" insufficiency of the regulatory TIM-3 checkpoint linked to post-aSCT IBD.

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.

Inborn Errors of Purine Salvage and Catabolism

Cellular purine nucleotides derive mainly from de novo synthesis or nucleic acid turnover and, only marginally, from dietary intake. They are subjected to catabolism, eventually forming uric acid in humans, while bases and nucleosides may be converted back to nucleotides through the salvage pathways. Inborn errors of the purine salvage pathway and catabolism have been described by several researchers and are usually referred to as rare diseases. Since purine compounds play a fundamental role, it is not surprising that their dysmetabolism is accompanied by devastating symptoms. Nevertheless, some of these manifestations are unexpected and, so far, have no explanation or therapy. Herein, we describe several known inborn errors of purine metabolism, highlighting their unexplained pathological aspects. Our intent is to offer new points of view on this topic and suggest diagnostic tools that may possibly indicate to clinicians that the inborn errors of purine metabolism may not be very rare diseases after all.

Case Report: Patient with deficiency of ADA2 presenting leukocytoclastic vasculitis and pericarditis during infliximab treatment

Deficiency of adenosine deaminase 2 (DADA2), first reported in 2014, is a disease with great phenotypic variability, which has been increasingly reported. Therapeutic response depends on the phenotype. We present a case of an adolescent with recurrent fever, oral aphthous ulcers, and lymphadenopathy from 8 to 12 years of age and subsequently presented with symptomatic neutropenia. After the diagnosis of DADA2, therapy with infliximab was started, but after the second dose, she developed leukocytoclastic vasculitis and showed symptoms of myopericarditis. Infliximab was switched to etanercept, with no relapses. Despite the safety of tumor necrosis factor alpha inhibitors (TNFi), paradoxical adverse effects have been increasingly reported. The differential diagnosis between disease new-onset manifestations of DADA2 and side effects of TNFi can be challenging and warrants further clarification.

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).

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.

LGL Clonal Expansion and Unexplained Cytopenia: Two Clues Don't Make an Evidence

Clonal expansions of large granular lymphocytes (LGL) have been reported in a wide spectrum of conditions, with LGL leukemia (LGLL) being the most extreme. However, the boundaries between LGLL and LGL clones are often subtle, and both conditions can be detected in several clinical scenarios, particularly in patients with cytopenias. The intricate overlap of LGL clonal expansion with other disease entities characterized by unexplained cytopenias makes their classification challenging. Indeed, precisely assigning whether cytopenias might be related to inadequate hematopoiesis (i.e., LGL as a marginal finding) rather than immune-mediated mechanisms (i.e., LGLL) is far from being an easy task. As LGL clones acquire different pathogenetic roles and relevance according to their diverse clinical settings, their detection in the landscape of bone marrow failures and myeloid neoplasms has recently raised growing clinical interest. In this regard, the current availability of different diagnostic techniques, including next generation sequencing, shed light on the relationship between LGL clones and cytopenias, paving the way towards a better disease classification for precision medicine treatments. Herein, we discuss the clinical relevance of LGL clones in the diagnostic algorithm to be followed in patients presenting with cytopenias, offering a foundation for rational management approaches.

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.