Clinical, imaging and genotypical features of three deceased and five surviving cases with ADA2 deficiency

Central retinal artery occlusion in a child with ADA2 deficiency: a case report

Introduction and importance

Deficiency of ADA2 (DADA2) is the first molecularly described monogenic vasculitis syndrome. During the past decade, DADA2's clinical spectrum has expanded significantly as the number of reported cases has increased.

Case presentation

A 5-year-old boy with DADA2 who experienced sudden onset left-sided vision loss due to unilateral central retinal artery occlusion. The patient had a history of recurrent fever and arthralgia with high inflammatory markers (C-reactive protein and erythrocyte sedimentation rate). Brain MRI showed mild limbic encephalitis, and MRA was normal. His gene sequencing results demonstrated substitutions mutation in ADA2, and the diagnosis of DADA2 was eventually confirmed.

Clinical discussion

Central retinal artery occlusion (CRAO) in paediatrics is a very rare condition. Typically, DADA2 presents in childhood as systemic inflammation, vasculitis, humoral immunodeficiency, and/or haematologic abnormalities. The most common phenotype described in the literature is vasculitis, which typically affects the skin and central nervous system, but other systems can also be affected. Ophthalmic manifestations are less common and highly variable.

Conclusions

DADA2 manifests rarely with central retinal artery occlusion; therefore, physicians should be aware of this manifestation.

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.

Adenosine deaminase 2 deficiency in a Chinese patient: Report of one novel mutation and literature review

OBJECTIVE

Through a case of deficiency of adenosine deaminase 2 (DADA2) to improve domestic clinicians' understanding of the disease, and to review the literature, promote dermatologists for clinical secondary primary lesion diagnosis.

METHOD

Analysis of a case diagnosed with DADA2 deficiency of clinical manifestations, laboratory, imaging examination and treatment methods, and discussion through literature analysis.

RESULTS

The child with recurrent fever, limbs nodular erythema, gradually in the limbs. CT of lower limb skin showed mild edema of the spinous layer, intact basal layer, dilated vascular congestion in the superficial dermis, visible RBC extravasation, and changes of telangiectasia ring purpura were considered. Cranial magnetic resonance imaging (MRI) showed a left choroidal cleft cyst. Genetic test was the CECR1 mutation. The treatment with adalimumab was effective.

CONCLUSION

In this case, DADA2 is the seventh case in China, and the CECR1 mutation site (c.254A> T p.N85I,c.851G>T p. G284V) was a compound heterozygous mutation. Mastering the clinical characteristics is helpful for clinicians to diagnose this disease.

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.

A new CECR1 mutation associated with severe hematological involvement in ADA2 deficiency

BACKGROUND

The deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessively inherited disease resulting from loss-of-function mutations in ADA2, formerly named CECR1 (cat eye syndrome chromosome region, candidate 1) gene. 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.

CASE PRESENTATION

We present a case of DADA2 deficiency with disease onset at 3 years old, not recognized till the age of 18 with severe gastrointestinal vasculitis and recurrent episodes of neutropenia associated with a new CECR1 mutation.

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.

A Cohort Study on Deficiency of ADA2 from China

PURPOSE

Deficiency of adenosine deaminase 2 (DADA2), an autosomal recessive autoinflammatory disorder caused by biallelic loss-of-function variants in adenosine deaminase 2 (ADA2), has not been systemically investigated in Chinese population yet. We aim to further characterize DADA2 cases in China.

METHODS

A retrospective analysis of patients with DADA2 identified through whole exome sequencing (WES) at seventeen rheumatology centers across China was conducted. Clinical characteristics, laboratory findings, genotype, and treatment response were analyzed.

RESULTS

Thirty patients with DADA2 were enrolled between January 2015 and December 2021. Adenosine deaminase 2 enzymatic activity was low in all tested cases to confirm pathogenicity. Median age of disease presentation was 4.3 years and the median age at diagnosis was 7.8 years. All but one patient presented during childhood and two subjects died from complications of their disease. The patients most commonly presented with systemic inflammation (92.9%), vasculitis (86.7%), and hypogammaglobinemia (73.3%) while one patient presented with bone marrow failure (BMF) with variable cytopenia. Twenty-three (76.7%) patients were treated with TNF inhibitors (TNFi), while two (6.7%) underwent hematopoietic stem cell transplantation (HSCT). They all achieved clinical remission. A total of thirty-nine ADA2 causative variants were identified, six of which were novel.

CONCLUSION

To establish early diagnosis and improve clinical outcomes, genetic screening and/or testing of ADA2 enzymatic activity should be performed in patients with suspected clinical features. TNFi is considered as first line treatment for those with vascular phenotypes. HSCT may be beneficial for those with hematological disease or in those who are refractory to TNFi.

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.

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.

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.

Clinical presentation of children with Deficiency of Adenosine deaminase 2: A case series

Deficiency of Adenosine deaminase 2 (DADA2) is a monogenic inflammatory disease, caused by mutations in ADA2 gene, which encodes an extracellular enzyme acting as a monocyte differentiation factor. DADA2 is first described with the clinical picture resembling polyarteritis nodosa, including livedo racemose, recurrent fever, musculoskeletal complaints. Besides, some patients have cytopenia, lymphoproliferation and mild to moderate immunodeficiency. The most crucial complication of DADA2 is neurological involvement, especially arterial stroke, which necessitates continuous treatment with anti-tumor necrosis factor α (anti-TNFα) treatment for preventing further stroke attacks. Herein, we report 5 DADA2 patients from 5 unrelated families, all had G47R mutation in at least one allele. All patients had livedo racemose, and 4 patients suffered from recurrent fever. Besides, musculoskeletal complaints and gastrointestinal symptoms were present in 4 and 3 patients, respectively. One patient had chronic arthritis and only one patient had a history of recurrent stroke without any sequela. Hematological and immunological involvement occurred in 3 and 4 patients, respectively, whereas only one had significant panhypogammaglobulinemia, requiring replacement therapy. We started etanercept treatment to all patients, which resulted the complete resolution of systemic inflammatory attacks and skin lesions and provided neurologically symptom free during their follow-up. With this report, we emphasize the importance of early referral of the patients with suspected livedo racemose to avoid the delay of DADA2 diagnosis for favorable outcome.

Evaluation of subclinical ocular involvement in patients with deficiency of adenosine deaminase 2 (DADA2)

PURPOSE

To evaluate changes in the peripapillary, macular, and choroidal microvasculature in the eyes of patients with deficiency of adenosine deaminase 2 (DADA2) and no clinical signs of ocular involvement.

METHODS

The study included 12 eyes of 12 patients with DADA2 and 24 eyes of 24 healthy subjects. The foveal avascular zone (FAZ), macular vessel densities (VDs) in the superficial and deep retinal capillary plexuses, peripapillary VDs, and choroidal thickness were evaluated by optical coherence tomography angiography (OCTA). Measurements were compared between DADA2 patients and healthy controls.

RESULTS

The median age was 17 (8-25) years in DADA2 patients and 17.5 (7-23) years in control group at the OCTA visit (p = 0.934). FAZ area did not differ between the groups (p = 0.224). In the superficial capillary plexus, whole-image, foveal, and parafoveal VD values were slightly lower in DADA2 patients than in controls (p = 0.054, p = 0.052, p = 0.117). In the deep capillary plexus, whole-image and parafoveal VD values were significantly lower in DADA2 patients than controls (p = 0.010, p = 0.001). VD in the radial peripapillary capillary plexus was also lower in DADA2 patients, with significantly lower peripapillary VD (p = 0.002). Subfoveal choroidal thickness was significantly higher in patients with DADA2 (p < 0.001).

CONCLUSIONS

This OCTA study demonstrates that both retinal and choroidal involvement may occur in DADA2 patients before the emergence of evident clinical findings.

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.

Novel Adenosine Deaminase 2 (ADA2) Mutations Associated With Hematological Manifestations

Recent progress in laboratory techniques, particularly, identification of novel disease-causing genes, has led to the detection of different gene mutations that might be implicated in the pathogenesis of different hematological disorders like pure red cell aplasia (PRCA) and neutropenia. An autoinflammatory disorder known as deficiency of adenosine deaminase 2 (DADA2) has been recently noticed to present with variable hematologic abnormalities. We report 2 patients who presented with hematologic abnormalities in which 2 ADA2 gene mutations were detected. The first case is a 5-year-old girl who presented with severe PRCA and autoimmune hemolytic anemia without any other manifestation of DADA2 that resulted from a novel CECR1 c.714_738dup, p. (Ala247Glnfs*16) homozygous variant. The second case is a 10-year-old boy, known to have Hodgkin lymphoma and was under follow-up for 6 years; he presented with persistent neutropenia and was discovered to be homozygous for ADA2 c.1447_1451del, p. (Ser483Profs*5). In conclusion, we report two different novels ADA2 variants in two children; the first presented with PRCA and the second presented with persistent neutropenia. This report aims to raise the concerns regarding the use of genetic testing in different hematologic diseases with indefinite etiology, as it will lead to the best therapeutic strategies without the need for unnecessary interventions.

Lentiviral correction of enzymatic activity restrains macrophage inflammation in adenosine deaminase 2 deficiency

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

The challenges of chronic urticaria part 2: Pharmacological treatment, chronic inducible urticaria, urticaria in special situations

This is Part 2 of an updated follow-up review of the World Allergy Organization (WAO) position paper on the diagnosis and treatment of urticaria and angioedema. Since that document was published, new advances in the understanding of the pathogenesis of chronic urticaria, and greater experience with the use of biologics in patients with severe refractory disease, mainly omalizumab, have been gained. For these reasons, WAO decided to initiate an update targeted to general practitioners around the world, incorporating the most recent information on epidemiology, immunopathogenesis, comorbidities, quality of life, clinical case presentations, and the management of chronic spontaneous and chronic inducible urticaria, and urticaria in special situations such as childhood and pregnancy. A special task force of WAO experts was invited to write the different sections of the manuscript, and the final document was approved by the WAO Board of Directors. This paper is not intended to be a substitute for current national and international guidelines on the management of urticaria and angioedema, but to provide an updated simplified guidance for physicians around the world who have to manage patients with this common ailment.

A Novel Variant of Adenosine Deaminase 2 Deficiency Presented With Chronic Thrombocytopenia, Anemia, and Early-Onset Stroke

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

A rare case of Polyarteritis Nodosa associated with autoimmune hepatitis: a case report

Background

Polyarteritis nodosa is a type of vasculitis affecting medium- and small-sized arteries that has been associated with hepatitis B but does not have an established relationship with autoimmune hepatitis. Here we report the case of an adult patient with autoimmune hepatitis who, shortly after diagnosis, developed life-threatening polyarteritis nodosa.

Case presentation

A 45-year-old woman was diagnosed with autoimmune hepatitis after initially presenting with a two-month history of fatigue, nausea, and anorexia and a three-week history of scleral icterus. Her liver biopsy showed mild portal fibrosis and her liver chemistries improved with prednisone and azathioprine. Three months later, she presented to the emergency department with fever, bilateral ankle pain, rash, oral ulcers, and poor vision. Physical examination was notable for erythema nodosum, anterior uveitis, retinal vasculitis, and frosted branch angiitis (frosted branch angiitis (a widespread florid translucent perivascular exudate). She subsequently developed repeated episodes of ischemic acute bowel necrosis that required multiple surgeries and extensive small bowel resections. Surgical pathology of the small bowel resection revealed ischemic necrosis, medium and small vessel vasculitis with microvascular thrombi consistent with polyarteritis nodosa. Azathioprine was discontinued and she was treated with pulse steroids followed by a prednisone taper, cyclophosphamide, and intravenous immune globulin with overall improvement in her symptomatology. Since her hospitalization, she has been maintained on low-dose prednisone and mycophenolate mofetil.

Conclusions

In patients with recent diagnosis of autoimmune hepatitis, there should be a modest suspicion for concomitant polyarteritis nodosa if symptoms and signs of multisystem vasculitis develop.

Vasculitic peripheral neuropathy in deficiency of adenosine deaminase 2

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive inflammatory vasculopathy characterized by systemic vasculitis, early-onset stroke and livedo racemosa. We report a family cohort of 3 patients with ADA2 compound heterozygous mutation p.[Thr360Ala] and [Gly383Ser]. Two of them had progressive involvement of the peripheral nervous system in the fourth decade, both after stroke. In one patient, clinical and neurophysiological studies showed progression of mononeuritis multiplex to chronic axonal sensorimotor polyneuropathy, nerve biopsy had features of small vessel vasculitic neuropathy, and muscle biopsy disclosed neurogenic atrophy with reinnervation. The second patient presented with progressive sensory symptoms of the lower limbs and chronic axonal sensorimotor polyneuropathy in nerve conduction studies. These two patients had absent plasma ADA2 activity. The third patient had no neurological affection despite low, but not absent, plasma ADA2 activity. Patients were started on a tumor necrosis factor (TNF) inhibitor, which has presumed benefits for the vasculitic phenotype of DADA2.

Case Report: An Adult Patient With Deficiency of Adenosine Deaminase 2 Resembled Unilateral Frosted Branch Angiitis

Purpose: Deficiency of adenosine deaminase 2 (DADA2) is a rare autosomal recessive systemic autoinflammatory disorder. We describe a rare case of an adult patient with DADA2 who presented with unilateral frosted branch angiitis (FBA) combined with branch retinal vein occlusion and panuveitis.

Method: This paper is a clinical case report.

Results: A 31-year-old male patient complained of blurred vision in his right eye for 2 days. His fundus examination showed FBA combined with branch retinal vein occlusion and panuveitis. He had a medical history of intermittent and recurrent fever, skin rash and aphthous ulcer for 5 years, and lacunar infarction for 1 month. Laboratory examinations showed hypogammaglobulinemia and mild prolonged activated partial thromboplastin time (APTT). Brain magnetic resonance imaging (MRI) revealed old lacunar infarction in the right basal ganglia and the lateral ventricle and fresh lacunar infarction in the right pons, respectively. The perivascular sheathing of FBA and macular edema were resolved after steroid administration and treatment of intravitreal anti-VEGF injection. During the period of follow-up, the patient subsequently suffered from recurrence of strokes, abnormality of coagulation function, sudden hearing loss of the left ear, and diplopia. His gene sequencing results demonstrated several deletion mutations in ADA2, and the diagnosis of DADA2 was eventually confirmed.

Conclusions: FBA represents a very rare ocular feature of DADA2 and may in some cases be the presenting manifestation. Therefore, ophthalmologists need to be aware of this rare autoinflammatory disease.

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.

Diagnosis and management of adenosine deaminase 2 deficiency children: the experience from China

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) is a rare autoinflammatory disease caused by mutations in the ADA2 gene. Few Chinese cases have been reported. We describe and compare the clinical features, genotypes, and treatments of Chinese DADA2 patients and non-Chinese patients.

METHODS

Primary immunodeficiency disease panel or whole-exome sequencing was performed for suspected cases, and assays for adenosine deaminase 2 (ADA2) enzyme activity were also carried out for the patients and their parents. Case reports of Chinese and non-Chinese patients with DADA2 were searched in PubMed and Chinese national databases.

RESULTS

Seven unrelated children from China with DADA2 were included in our study. Five were identified at Peking Union Medical College Hospital, and two had been reported previously (1 on PubMed and 1 in Chinese literature). Fourteen mutations in ADA2 were identified, 7 of which have not previously been reported in non-Chinese patients. Four children who underwent enzymatic analysis had lower ADA2 activity compared with their parents. Phenotypic manifestations included fever, skin symptoms, vasculitis, and neurologic involvement. Treatments varying from steroids, immunosuppressants, and tocilizumab, anti-TNF therapy and hematopoietic stem cell transplantation (HSCT) were effective depending on phenotype and severity.

CONCLUSION

This study includes the largest number of Chinese DADA2 patients to date. We recommend the combination of enzymatic analysis with gene screening to confirm the diagnosis. Different genotypes were observed among Chinese DADA2 patients; most phenotypes were similar to those of non-Chinese DADA2 patients, except for growth retardation. Disease remission might not be achieved with anti-IL-6 therapy.

Widening the Neuroimaging Features of Adenosine Deaminase 2 Deficiency

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

Deficiency of Adenosine Deaminase 2 in Adults and Children: Experience From India

OBJECTIVE

Deficiency of adenosine deaminase 2 (DADA2) is a potentially fatal monogenic syndrome characterized by variable manifestations of systemic vasculitis, bone marrow failure, and immunodeficiency. Most cases are diagnosed by pediatric care providers, given the typical early age of disease onset. This study was undertaken to describe the clinical phenotypes and treatment response both in adults and in children with DADA2 in India.

METHODS

A retrospective analysis of pediatric and adult patients with DADA2 diagnosed at various rheumatology centers across India was conducted. Clinical characteristics, diagnostic findings, and treatment responses were analyzed in all subjects.

RESULTS

In total, 33 cases of DADA2 were confirmed in this cohort between April 2017 and March 2020. Unlike previous studies, nearly one-half of the confirmed cases presented during adulthood. All symptomatic patients exhibited features of vasculitis, whereas constitutional symptoms and anemia were more common in pediatric patients. Cutaneous and neurologic involvement were common, and 18 subjects had experienced at least one stroke. In addition, the clinical spectrum of DADA2 was expanded by recognition of novel features in these patients, including pancreatic infarction, focal myocarditis, and diffuse alveolar hemorrhage. Treatment with tumor necrosis factor inhibitors (TNFi) was initiated in 25 patients. All of the identified disease manifestations showed marked improvement after initiation of TNFi, and disease remission was achieved in 19 patients. Two cases were complicated by tuberculosis infection, and 2 deaths were reported.

CONCLUSION

This report presents the first case series of patients with DADA2 from India, diagnosed by adult and pediatric care providers. The findings raise awareness of this syndrome, particularly with regard to its presentation in adults.

Monogenic autoinflammatory disorders: beyond the periodic fever

The past two decades have seen an exponential increase in the number of monogenic autoinflammatory disorders described, coinciding with improved genetic sequencing techniques. This group of disorders has evolved to be heterogeneous and certainly more complex than the original four 'periodic fever syndromes' caused by innate immune over-activation. This review aims to provide an update on the classic periodic fever syndromes as well as introducing the broadening spectrum of clinical features seen in more recently described conditions.

The Many Faces of a Monogenic Autoinflammatory Disease: Adenosine Deaminase 2 Deficiency

PURPOSE OF REVIEW

We aim to describe the pathophysiology, clinical findings, diagnosis, and treatment of deficiency of adenosine deaminase 2 (DADA2).

RECENT FINDINGS

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

Two cases of ADA2 deficiency presenting as childhood polyarteritis nodosa: novel ADA2 variant, atypical CNS manifestations, and literature review

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease resulting from loss-of-function pathogenic variants in ADA2 gene, which might resemble polyarteritis nodosa (PAN). The authors present two pediatric cases of ADA2 deficiency with phenotypic manifestations of PAN, including an unusual presentation with spinal cord ischemia. Also described is an assessment of ADA2 activity and gene expression profiling with description of a previously unreported homozygous variant, c.1226C > A (p.(Pro409His)), detected in a patient with consanguineous parents, confirmed by near-absent ADA2 plasma enzymatic activity. The authors suggest to first obtain enzymatic activity, whenever DADA2 is suspected, before proceeding to genetic testing, due to its excellent cost-effective results. Moreover, physicians must be aware of this monogenic disorder, especially in the case of early-onset PAN-like manifestations, having a family member with similar manifestations or having consanguineous parents suggesting an autosomal recessive inheritance pattern. Given the multi-organ involvement, recognizing the diverse manifestations is a crucial step towards timely diagnosis and management of this potentially fatal but often treatable syndrome.

Choroidal vascularity index as a biomarker of systemic inflammation in childhood Polyarteritis Nodosa and adenosine deaminase-2 deficiency

BACKGROUND/PURPOSE

To assess EDI-OCT (enhanced depth imaging optical coherence tomography) of choroid for inflammatory signs in children with polyarteritis nodosa (PAN) and adenosine deaminase-2 deficiency (DADA-2).

METHODS

In this cross-sectional study conducted between June 2017 and September 2018, we evaluated children diagnosed with PAN (n = 11) and DADA-2 (n = 4) and an age- and sex-matched control group (n = 15). Demographic and laboratory data were retrospectively analyzed from patient charts. Disease activity was assessed using the pediatric vasculitis activity score (PVAS). Choroidal images were obtained with spectral domain-OCT to measure choroidal thickness (ChT) at 5 points (750 and 1500 μm from the foveal center in the temporal and nasal quadrants and beneath the fovea), and to calculate the total subfoveal choroidal area (TCA), luminal area (LA), stromal area (SA), and the choroidal vascularity index (CVI).

RESULTS

The median (min-max) age was 8 (4-16) years in PAN patients, 6 (5-16) years in DADA-2 patients and 8 (8-10) years in control group at the OCT visit (p = 0.214). The ChT at 3 points and the TCA, LA, and SA were higher in children with both PAN and DADA-2 patients compared to those of the control group (p < 0.0001, p = 0.049, p = 0.007, p = 0.007, p = 0.006, p = 0.033, respectively). The CVI was similar in both groups. No association was observed between the OCT findings, PVAS, and the erythrocyte sedimentation rate, and serum leukocyte and C-reactive protein levels.

CONCLUSION

Similar CVI scores were obtained from PAN and DADA2 patients under treatment and from healthy controls. Increased subfoveal ChT without any other signs of ocular involvement may suggest choroidal thickening as a sign of mild subclinical inflammation.

Autoinflammatory diseases in childhood, part 1: monogenic syndromes

Autoinflammatory diseases constitute a family of disorders defined by aberrant stimulation of inflammatory pathways without involving antigen-directed autoimmunity. They may be divided into monogenic and polygenic types. Monogenic autoinflammatory syndromes are those with identified genetic mutations, such as familial Mediterranean fever, tumor necrosis factor receptor-associated periodic fever syndrome (TRAPS), mevalonate kinase deficiency or hyperimmunoglobulin D syndrome, cryopyrin-associated periodic fever syndromes (CAPS), pyogenic arthritis pyoderma gangrenosum and acne (PAPA) syndrome, interleukin-10 and interleukin-10 receptor deficiencies, adenosine deaminase 2 deficiency and pediatric sarcoidosis. Those without an identified genetic mutation are known as polygenic and include systemic-onset juvenile idiopathic arthritis, idiopathic recurrent acute pericarditis, Behçet syndrome, chronic recurrent multifocal osteomyelitis and inflammatory bowel disease among others. Autoinflammatory disorders are defined by repeating episodes or persistent fever, rash, serositis, lymphadenopathy, arthritis and increased acute phase reactants, and thus may mimic infections clinically. Most monogenic autoinflammatory syndromes present in childhood. However, because of their infrequency, diverse and nonspecific presentation, and the relatively new genetic recognition, diagnosis is usually delayed. In this article, which is Part 1 of a two-part series, the authors update monogenic autoinflammatory diseases in children with special emphasis on imaging features that may help establish the correct diagnosis.

A 9.5-year-old boy with recurrent neurological manifestations and severe hypertension, treated initially for polyarteritis nodosa, was subsequently diagnosed with adenosine deaminase type 2 deficiency (DADA2) which responded to anti-TNF-α

A 9.5-year-old boy was referred with a 2-year history of recurrent fever, myalgia, abdominal pain and various neurological manifestations associated with increased acute phase reactants and IgG level. During the recent episode, severe hypertension and right-sided hemiparesis developed and angiography demonstrated irregularities and stenosis in renal and mesenteric artery branches. Although these manifestations were consistent with polyarteritis nodosa (PAN), the consanguinity of his parents, a cousin with similar clinical features and early disease onset led to suspicion of deficiency of adenosine deaminase type 2 (DADA2) diseases. DADA2 was established by demonstration of decreased ADA2 enzyme activity and a homozygous G47R mutation in the CECR1 gene. The diagnosis of DADA2 is challenging because of the overlapping manifestations with PAN and other periodic fever syndromes. DADA2 should be considered in the differential diagnosis of PAN. Raised IgG levels (usually low in DADA2) should be sought in future cases.Abbreviations: CECR1, cat eye syndrome chromosome region candidate 1; DADA2, deficiency of adenosine deaminase type 2; MEFV, Mediterranean fever; PAN, polyarteritis nodosa.

Genotype and functional correlates of disease phenotype in deficiency of adenosine deaminase 2 (DADA2)

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) is a syndrome with pleiotropic manifestations including vasculitis and hematologic compromise. A systematic definition of the relationship between adenosine deaminase 2 (ADA2) mutations and clinical phenotype remains unavailable.

OBJECTIVE

We sought to test whether the impact of ADA2 mutations on enzyme function correlates with clinical presentation.

METHODS

Patients with DADA2 with severe hematologic manifestations were compared with vasculitis-predominant patients. Enzymatic activity was assessed using expression constructs reflecting all 53 missense, nonsense, insertion, and deletion genotypes from 152 patients across the DADA2 spectrum.

RESULTS

We identified patients with DADA2 presenting with pure red cell aplasia (n = 5) or bone marrow failure (BMF, n = 10) syndrome. Most patients did not exhibit features of vasculitis. Recurrent infection, hepatosplenomegaly, and gingivitis were common in patients with BMF, of whom half died from infection. Unlike patients with DADA2 with vasculitis, patients with pure red cell aplasia and BMF proved largely refractory to TNF inhibitors. ADA2 variants associated with vasculitis predominantly reflected missense mutations with at least 3% residual enzymatic activity. In contrast, pure red cell aplasia and BMF were associated with missense mutations with minimal residual enzyme activity, nonsense variants, and insertions/deletions resulting in complete loss of function.

CONCLUSIONS

Functional interrogation of ADA2 mutations reveals an association of subtotal function loss with vasculitis, typically responsive to TNF blockade, whereas more extensive loss is observed in hematologic disease, which may be refractory to treatment. These findings establish a genotype-phenotype spectrum in DADA2.

ADA2 Deficiency: Case Series of Five Patients with Varying Phenotypes

OBJECTIVE

To describe the clinical features, genotype, and treatment approaches of patients with confirmed adenosine deaminase 2 (ADA2) deficiency with dissimilar phenotypes.

METHODS

A case series of five DADA2 patients from three families was presented. The clinical and laboratory data, treatment protocols, and outcome of the patients were recorded from the patients' medical charts. ADA2 gene was screened by next generation sequencing first and then verified by Sanger sequencing. Serum ADA2 enzyme activity was measured by modified spectrophotometric method.

RESULTS

The median (min-max) age at onset of symptoms and age at diagnosis were 11 (9-13.8) years and 15 (9-19) years, respectively. The median (min-max) follow-up period was 8 (6-45) months. There was consanguinity in two families (2/3). The main clinical manifestations are musculoskeletal (5/5), dermatological (4/5), and neurological (2/5). Homozygosity for the p.G47R mutation in ADA2 gene was detected in three patients. A homozygous mutation in ADA2 gene (c.650 T > A; p.Val217Asp) was detected in two siblings. Plasma ADA2 enzymatic activity was absent in all patients. Anti-tumor necrosis factor (TNF) therapy was commenced, and all patients became clinically inactive with normal acute-phase reactants.

CONCLUSION

ADA2 mutations should be checked in patients with presence of inflammation and livedoid vasculitis when they have neurological findings, especially in the form of stroke; and a history suggesting for an inherited disease; or presence of resistance to conventional treatment. Besides, anti-TNF seems to be useful for treatment of DADA2.

Role of adenosine deaminase 2 gene variants in pediatric deficiency of adenosine deaminase 2: A structural biological approach

Adenosine deaminase 2 (ADA2) belongs to the novel family of adenosine deaminase growth factors (ADGFs), which play an important role in tissue development. The deficiency of adenosine deaminase 2 (DADA2) is a recently recognized autosomal recessive autoinflammatory disease, characterized by various systemic vascular and inflammatory manifestations, which is associated with ADA2 mutations. Considering that a recent screening of an international registry of children with systemic primary vasculitis revealed novel and already known variants in ADA2, this study aimed to further investigate the functional significance of the rare variants detected, namely p.Gly47Arg, p.Gly47Ala, p.Arg8Trp, p.Leu351Gln and p.Ala357Thr, by using a structural biological approach. Three-dimensional models of the mutants were developed and their three-dimensional (3D) structures were subjected to detailed interaction and conformational analyses. This led to suggestions that the novel mutations found may affect the formation/stability of the homodimer or may influence the activity of the enzyme. It was thus concluded that the Arg8Trp and Gly47Arg mutations affect the position and interaction of the dimer-associated HN1 helical structure and therefore, dimer formation and stabilization, while Leu351Gln and Ala357Thr influence the metal coordination in the active site. These findings shed further light onto the structural consequences of the mutations under investigation.

Human adenosine deaminase 2 deficiency: A multi-faceted inborn error of immunity

Human adenosine deaminase 1 deficiency was described in the 1970s to cause severe combined immunodeficiency. The residual adenosine deaminase activity in these patients was attributed to adenosine deaminase 2. Human adenosine deaminase type 2 deficiency (DADA2), due to biallelic deleterious mutations in the ADA2 gene, is the first described monogenic type of small- and medium-size vessel vasculitis. The phenotype of DADA2 also includes lymphoproliferation, cytopenia, and variable degrees of immunodeficiency. The physiological role of ADA2 is still enigmatic hence the pathophysiology of the condition is unclear. Preliminary data showed that in the absence of ADA2, macrophage differentiation is skewed to a pro-inflammatory M1 subset, which is detrimental for endothelial integrity. The inflammatory phenotype responds well to anti-TNF therapy with etanercept and that is the first-line treatment for prevention of severe vascular events including strokes. The classic immunosuppressive drugs are not successful in controlling the disease activity. However, hematopoietic stem cell transplantation (HSCT) has been shown to be a definitive cure in DADA2 patients who present with a severe cytopenia. HSCT can also cure the vascular phenotype and is the treatment modality for patients' refractory to anti-cytokine therapies. In this review, we describe what is currently known about the molecular mechanisms of DADA2. Further research on the pathophysiology of this multifaceted condition is needed to fine-tune and steer future therapeutic strategies.

A homozygote novel L451W mutation in CECR1 gene causes deficiency of adenosine deaminase 2 in a pediatric patient representing with chronic lymphoproliferation and cytopenia

Deficiency of Adenosine Deaminase 2 (DADA2) is a monogenic autoinflammatory disorder characterized by livedo reticularis, skin ulcers, subcutaneous rash, aphthous ulcers, and leukocytoclastic vasculitis, neurological signs such as early onset stroke and polyneuropathy. A minority of DADA2 patients suffer from severe cytopenia and lymphoproliferation. Herein, we report an adolescent patient, followed up as having a hematological disorder for many years, eventually diagnosed as having DADA2. In view of the presence of elevated acute phase reactants, hepatosplenomegaly, low IgM level, lymphopenia, anemia, and neutropenia, and a subtle neurological involvement we considered DADA2 diagnosis. The diagnosis was confirmed by identification of a novel L451W mutation in CECR1 gene. The patient has been successfully treated with etanercept, monthly intravenous immunoglobulin replacement, and low-dose methylprednisolone. In conclusion, although the absence of skin and neurological findings, low IgM levels, and persistent lymphopenia should lead the physicians to consider DADA2 in patients with particularly complicated hematological abnormalities.

A Child Diagnosed With Treatment-Resistant Polyarteritis Nodosa: Can the Clinical Diagnosis Be Different?

Polyarteritis nodosa (PAN) is a necrotizing systemic vasculitis involving the wall of small and medium sized arteries. The histological aspect is defined by the presence of fibrinoid necrosis and an infiltrate rich in neutrophil polynuclears in the artery wall and rare granulomas. CECR1 (Cat Eye Syndrome Chromosome Region 1) gene mutation causing adenosine deaminase 2 (ADA2) deficiency is also associated with systemic inflammation, vasculopathy, and frequently PAN. Strokes, neurological involvement, and gastrointestinal involvement have poor prognosis in the cases with ADA2 deficiency particularly in early stage. In this article, we report a 17-year-old male patient diagnosed with PAN who had severe gastrointestinal system involvement that was resistant to intensive and conventional immunosuppressive treatment and showed a fatal course despite the emergency surgical intervention. After the patient was exitus, he was detected to have a heterozygous mutation (V276A) of familial Mediterranean fever (FMF) and also a homozygous ADA2 mutation. The aim of this article is to highlight that ADA2 deficiency may be present in treatment-resistant PAN cases who apply due to severe systemic involvement. In this case, accompanying FMF mutation was also observed.

"Immune" Thrombocytopenia as Key Feature of a Novel ADA2 Deficiency Variant: Implication on Differential Diagnostics of ITP in Children

Thrombocytopenia presenting during early childhood is most commonly diagnosed as immune/idiopathic thrombocytopenic purpura (ITP), where the antibody-mediated destruction of thrombocytes is often transient. If treatment is indicated, the majority of patients respond to immune-modulation by intravenous immunoglobulin G infusion or systemic corticosteroids. Differential diagnoses to childhood ITP includes thrombocytopenia due to infections, drugs, rheumatologic conditions, immune dysregulation, and inherited bone marrow failures, for example, congenital amegakaryocytic thrombocytopenia. Isolated thrombocytopenia in an otherwise healthy appearing child that recurs after therapy and/or persists suggest a differential diagnosis rather than ITP. We present a case of symptomatic thrombocytopenia in a 2-year-old girl associated with adenosine deaminase deficiency.

Skin disorders are prominent features in primary immunodeficiency diseases: A systematic overview of current data

Primary immunodeficiency diseases (PIDs) are characterized by an increased risk of infections, autoimmunity, autoinflammation, malignancy, and allergic disorders. Skin disorders are also common clinical features in PIDs and may be among the presenting manifestations. Recognition of specific PID-associated skin conditions in combination with other clinical features as described in the currently used warning signs could raise suspicion of an underlying PID. We aimed to provide a systematically obtained overview of skin disorders and their prevalence in PIDs. Secondary, the prevalence of Staphylococcus (S.) aureus-associated skin disorders and atopy was reviewed, as these are the most prominent skin features in PIDs. A systematic search was performed in EMBASE, MEDLINE, Web of Science, Cochrane, and Google Scholar (up to May 9, 2018). All original observational and experimental human studies that address the presence of skin disorders in PIDs were selected. We rated study quality using the Institute of Health Economics Quality Appraisal Checklist for Case Series Studies. Sixty-seven articles (5030 patients) were included. Study quality ranged from 18.2% to 88.5%. A broad spectrum of skin disorders was reported in 30 PIDs, mostly in single studies with a low number of included patients. An overview of associated PIDs per skin disorder was generated. Data on S. aureus-associated skin disorders and atopy in PIDs were limited. In conclusion, skin disorders are prominent features in PIDs. Through clustering of PIDs per skin disorder, we provide a support tool to use in clinical practice that should raise awareness of PIDs based on presenting skin manifestations.

ALPS-Like Phenotype Caused by ADA2 Deficiency Rescued by Allogeneic Hematopoietic Stem Cell Transplantation

Adenosine deaminase 2 (ADA2) deficiency is an auto-inflammatory disease due to mutations in cat eye syndrome chromosome region candidate 1 (CECR1) gene, currently named ADA2. The disease has a wide clinical spectrum encompassing early-onset vasculopathy (targeting skin, gut and central nervous system), recurrent fever, immunodeficiency and bone marrow dysfunction. Different therapeutic options have been proposed in literature, but only steroids and anti-cytokine monoclonal antibodies (such as tumor necrosis factor inhibitor) proved to be effective. If a suitable donor is available, hematopoietic stem cell transplantation (HSCT) could be curative. Here we describe a case of ADA2 deficiency in a 4-year-old Caucasian girl. The patient was initially classified as autoimmune neutropenia and then she evolved toward an autoimmune lymphoproliferative syndrome (ALPS)-like phenotype. The diagnosis of ALPS became uncertain due to atypical clinical features and normal FAS-induced apoptosis test. She was treated with G-CSF first and subsequently with immunosuppressive drugs without improvement. Only HSCT from a 9/10 HLA-matched unrelated donor, following myeloablative conditioning, completely solved the clinical signs related to ADA2 deficiency. Early diagnosis in cases presenting with hematological manifestations, rather than classical vasculopathy, allows the patients to promptly undergo HSCT and avoid more severe evolution. Finally, in similar cases highly suspicious for genetic disease, it is desirable to obtain molecular diagnosis before performing HSCT, since it can influence the transplant procedure. However, if HSCT has to be performed without delay for clinical indication, related donors should be excluded to avoid the risk of relapse or partial benefit due to a hereditary genetic defect.

Pediatric rheumatology in Turkey

Pediatric Rheumatology is an emerging specialty in Turkey with increasing number of available centers and specialists all over the country. In this paper, we sought to provide an overview on pediatric rheumatology service in our country, as well as to assess the principle published literature from Turkey in this field. A systematic literature search has been performed to achieve the significance and the impact of this manuscript. The most relevant used databases (PubMed/MEDLINE, Web of Science, SCOPUS) for peer-reviewed studies and reviews in English language published during the last 5 years were screened. In the first part of the manuscript, we tried to give more details on the history of pediatric rheumatology in Turkey. In further text, we put an accent over the most common rheumatologic conditions among children in Turkey, including Familial Mediterranean fever, juvenile idiopathic arthritis, juvenile spondyloarthropathies, and childhood vasculitides. Despite the considerable literature from Turkey on pediatric rheumatic diseases, a need for unique strategies that would guide the management of rheumatic diseases in childhood remains open. The cultural and historical inheritance together with geographical position make the Turkey a suitable ground for investigations in filed of auto-inflammation and all other inflammatory conditions. Prospective, multicentric studies especially among rheumatologic conditions common in this part of the world would give us more relevant data and open new horizons in diseases' management. International collaborations and databases should be highly encouraged and supported, to make the care of pediatric rheumatic disease uniform.

Renal Amyloidosis in Deficiency of Adenosine Deaminase 2: Successful Experience With Canakinumab

Deficiency of adenosine deaminase 2 (DADA2) is a rare autoinflammatory disease that was firstly described in patients with early-onset strokes, livedo reticularis, and periodic fever resembling polyarteritis nodosa. In reported case series, researchers described highly variable manifestations, including autoimmunity, immunodeficiency, hepatosplenomegaly, pancytopenia, ichthyosiform rash, and arthritis, in patients with DADA2. A thirteen-year-old female patient who was born to consanguineous parents was admitted to our hospital with generalized edema and leg pain. A physical examination revealed splenomegaly and left knee arthritis. Nephrotic-range proteinuria and hypoalbuminemia were present, and a renal biopsy revealed amyloidosis. Despite the absence of periodic fever and livedo reticularis, our patient had suggestive features of DADA2, including low serum immunoglobulin G and immunoglobulin M levels, hepatosplenomegaly, and renal amyloidosis. We found a heterozygote Met694Val mutation in the Mediterranean fever gene and a novel homozygote Thr317Argfs*25 (c.950-950delCys) mutation in the cat eye chromosome region 1 gene. A functional analysis revealed absent plasma adenosine deaminase 2 activity. Canakinumab was administered because of unresponsive proteinuria despite 2 months of treatment with colchicine and methylprednisolone. Proteinuria improved after 7 doses of canakinumab. In conclusion, DADA2 should be considered in the differential diagnosis of renal amyloidosis, particularly in the absence of homozygote Mediterranean fever mutations. Although anti-tumor necrosis factor agents are widely offered in DADA2 treatment, we speculate that canakinumab may be an appropriate treatment of renal amyloidosis in DADA2.

The classification, genetic diagnosis and modelling of monogenic autoinflammatory disorders

Monogenic autoinflammatory disorders are an increasingly heterogeneous group of conditions characterised by innate immune dysregulation. Improved genetic sequencing in recent years has led not only to the discovery of a plethora of conditions considered to be 'autoinflammatory', but also the broadening of the clinical and immunological phenotypic spectra seen in these disorders. This review outlines the classification strategies that have been employed for monogenic autoinflammatory disorders to date, including the primary innate immune pathway or the dominant cytokine implicated in disease pathogenesis, and highlights some of the advantages of these models. Furthermore, the use of the term 'autoinflammatory' is discussed in relation to disorders that cross the innate and adaptive immune divide. The utilisation of next-generation sequencing (NGS) in this population is examined, as are potential in vivo and in vitro methods of modelling to determine pathogenicity of novel genetic findings. Finally, areas where our understanding can be improved are highlighted, such as phenotypic variability and genotype-phenotype correlations, with the aim of identifying areas of future research.

Deficiency of Adenosine Deaminase 2 (DADA2): Updates on the Phenotype, Genetics, Pathogenesis, and Treatment

Deficiency of ADA2 (DADA2) is the first molecularly described monogenic vasculitis syndrome. DADA2 is caused by biallelic hypomorphic mutations in the ADA2 gene that encodes the adenosine deaminase 2 (ADA2) protein. Over 60 disease-associated mutations have been identified in all domains of ADA2 affecting the catalytic activity, protein dimerization, and secretion. Vasculopathy ranging from livedo reticularis to polyarteritis nodosa (PAN) and life-threatening ischemic and/or hemorrhagic stroke dominate the clinical features of DADA2. Vasculitis and inflammation can affect many organs, explaining the intestinal, hepatological, and renal manifestations. DADA2 should be primarily considered in patients with early-onset fevers, rashes, and strokes even in the absence of positive family history. Hematological manifestations include most commonly hypogammaglobulinemia, although pure red cell aplasia (PRCA), immune thrombocytopenia, and neutropenia have been increasingly reported. Thus, DADA2 may unify a variety of syndromes previously not thought to be related. The first-line treatment consists of TNF-inhibitors and is effective in controlling inflammation and in preserving vascular integrity. Hematopoietic stem cell transplantation (HSCT) has been successful in a group of patients presenting with hematological manifestations. ADA2 is highly expressed in myeloid cells and plays a role in the differentiation of macrophages; however, its function is still largely undetermined. Deficiency of ADA2 has been linked to an imbalance in differentiation of monocytes towards proinflammatory M1 macrophages. Future research on the function of ADA2 and on the pathophysiology of DADA2 will improve our understanding of the condition and promote early diagnosis and targeted treatment.

Diagnosis and management of ADA2 deficient polyarteritis nodosa

Deficiency of ADA2 (DADA2) is a recently described systemic inflammatory vasculopathy caused by mutations in the CERC1 gene that often, but not always, clinically resembles polyarteritis nodosa (PAN). The condition was originally characterized by livedoid rash, systemic inflammation, variable hypogammaglobulinemia, and early-onset stroke. The phenotypic spectrum has expanded to include patients with immunodeficiency syndromes and bone marrow dysfunction, which are not typical features of PAN. Exploration into the pathogenesis and treatment options of DADA2 has added to our understanding of this condition, but more studies are needed. The purpose of this article is to review the various clinical phenotypes of DADA2, and raise awareness among rheumatologists to consider DADA2 when evaluating patients presenting with PAN-like disease.

Vasculopathy, Immunodeficiency, and Bone Marrow Failure: The Intriguing Syndrome Caused by Deficiency of Adenosine Deaminase 2

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic form of systemic vasculopathy that often presents during early childhood. Linked to biallelic mutations in ADA2 (previously CECR1), DADA2 was initially described as a syndrome of recurrent fever, livedo racemosa, early-onset strokes, and peripheral vasculopathy that resembles polyarteritis nodosum. However, the wide spectrum of clinical findings and heterogeneity of disease, even among family members with identical mutations, is increasingly recognized. Evidence of systemic inflammation and vasculopathy is not uniformly present in DADA2 patients and some can remain asymptomatic through adulthood. Humoral immunodeficiency characterized by low immunoglobulin levels and increased risk of infection is another common feature of DADA2. Variable cytopenias including pure red cell aplasia that mimics Diamond-Blackfan anemia can also be primary manifestations of DADA2. How defects in a single gene translate into these heterogeneous presentations remains to be answered. In this review, we will summarize lessons learned from the pleiotropic clinical manifestations of DADA2.