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.

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%.

Case Report: Consistent disease manifestations with a staggered time course in two identical twins affected by adenosine deaminase 2 deficiency.

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, including vasculitis, immunodeficiency, and hematologic manifestations, potentially progressing over time. The present study describes the long-term evolution of the immuno-hematological features and therapeutic challenge of two identical adult twin sisters affected by DADA2. The absence of plasmatic adenosine deaminase 2 (ADA2) activity in both twins suggested the diagnosis of DADA2, then confirmed by genetic analysis. Exon sequencing revealed a missense (p.Leu188Pro) mutation on the paternal ADA2 allele. While, whole genome sequencing identified an unreported deletion (IVS6_IVS7del*) on the maternal allele predicted to produce a transcript missing exon 7. The patients experienced the disease onset during childhood with early strokes (Patient 1 at two years, Patient 2 at eight years of age), subsequently followed by other shared DADA2-associated features, including neutropenia, hypogammaglobulinemia, reduced switched memory B cells, inverted CD4:CD8 ratio, increased naïve T cells, reduced follicular regulatory T cells, the almost complete absence of NK cells, T-large granular cell leukemia, and osteoporosis. Disease evolution differed: clinical manifestations presented several years earlier and were more pronounced in Patient 1 than in Patient 2. Due to G-CSF refractory life-threatening neutropenia, Patient 1 successfully underwent an urgent hematopoietic stem cell transplantation (HSCT) from a 9/10 matched unrelated donor. Patient 2 experienced a similar, although delayed, disease evolution and is currently on anti-TNF therapy and anti-infectious prophylaxis. The unique cases confirmed that heterozygous patients with null ADA2 activity deserve deep investigation for possible structural variants on a single allele. Moreover, this report emphasizes the importance of timely recognizing DADA2 at the onset to allow adequate follow-up and detection of disease progression. Finally, the therapeutic management in these identical twins raises significant concerns as they share a similar phenotype, with a delayed but almost predictable disease evolution in one of them, who could benefit from a prompt definitive treatment like elective allogeneic HSCT. Additional data are required to assess whether the absence of enzymatic activity at diagnosis is associated with hematological involvement and is also predictive of bone marrow dysfunction, encouraging early HSCT to improve functional outcomes.

A Case of Deficiency of Adenosine Deaminase 2: 28 years of Diagnostic Challenges.

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

The same mutation in a family with adenosine deaminase 2 deficiency.

The deficiency of adenosine deaminase 2 (DADA2) has recently been defined as a monogenetic autosomal recessive autoinflammatory disease. DADA2 is mainly characterized by high fever, livedo racemose, early-onset stroke, mild immunodeficiency and clinically polyarteritis nodosa (PAN)-like symptoms. Mutations in CECR1 (cat eye syndrome chromosome region, candidate 1) are responsible for DADA2. Livedoid racemose, lacunar infarct due to involvement in small vessel of the central nervous system, peripheral neuropathy, digital ulcers and loss of fingers are predominantly seen in the disease which could progress to end-stage organ failure and death in some patients. A wide spectrum of severity in phenotype as well as in the age of onset has been reported in the literature. This phenotypic variability is also found in our clinical practice even in patients with the same mutation. Here, we present a family diagnosed with DADA2, with the previously reported p.Gly47Arg mutation in CECR1.

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.

Clusters in Pediatric Rheumatic Diseases.

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

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 Monogenic Disease with a Variety of Phenotypes: Deficiency of Adenosine Deaminase 2.

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

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.

A Chinese DADA2 patient: report of two novel mutations and successful HSCT.

Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by autosomal recessive mutations in Cat Eye Syndrome Chromosome Region 1 (CECR1) gene. In this report, we aimed to describe the clinical manifestations, immunological features, genotype, and treatments of one Chinese patient with novel CECR1 gene mutations. This patient initially presented with recurrent fever and rashes from the age of 3 months, but no pathogen was found. She then developed dry gangrene of the fingers at 5 months of age. Laboratory examinations revealed elevated levels of C-reactive protein and thrombocytes. The expression of interleukin-6 (IL-6) and IL-8 were both elevated. Sequencing results revealed that she had compound heterozygous mutations in CECR1 gene (c.1211T>C, p.Phe404Ser and c.1114 G>A, p.Val372Met). Subsequently, treatment with anti-IL-6 (tocilizumab) was started. However, she developed blurred vision in the right eye with occlusion of the central retinal artery, accompanied by unsteady gait. Magnetic resonance imaging (MRI) showed infarction of the right thalamus. Finally, she underwent hematopoietic stem cell transplantation (HSCT) and is currently in remission. Our findings suggest that HSCT could cure this disease.

Deficiency of Adenosine Deaminase 2 in Adult Siblings: Many Years of a Misdiagnosed Disease With Severe Consequences.

OBJECTIVE: Describe the clinical characteristics and histopathology findings in a family with two siblings affected with deficiency of adenosine deaminase 2 (DADA2). Both patients presented in childhood with polyarthritis and developed significant neurological and gastrointestinal features of DADA2 in ear, including variable degrees of immunologic and hematologic manifestations. METHODS: Adenosine Deaminase 2 (ADA2; also known as cat eye syndrome chromosome region, candidate 1 gene; CECR1) exon sequencing and serum ADA2 levels were performed to confirm the diagnosis of DADA2. Comparison of serum adenosine deaminase 2 levels was made to DADA2 patients, carriers, and healthy controls in Patient 2. Autopsy specimens from brain and liver tissues were submitted for analysis. RESULTS: Both patients were found to carry a previously reported rare intronic missense mutation predicted to affect the transcript splicing (c.973-2A > G; rs139750129) and an unreported missense mutation p.Val458Asp (c.1373T > A; V458D). Both brothers started therapy with a tumor necrosis factor inhibitor following the molecular diagnosis of DADA2 with good response and were eventually tapered off prednisone. However, Patient 1 died 18 months later due to complications of end-stage liver disease. His autopsy showed evidence for nodular hyperplasia of the liver often seen in common variable immunodeficiency (CVID) and numerous small, old infarcts throughout the brain that had not been demonstrated on prior MRI/MRA imaging. CONCLUSION: These cases emphasize the importance of recognition of DADA2 in adults, compare CNS imaging modalities to pathologic findings and suggest similarities in liver pathology between DADA2 and CVID. MRI may not be most sensitive method to identify small subcortical infarcts in patients suspected to have DADA2.

Human adenosine deaminases ADA1 and ADA2 bind to different subsets of immune cells.

At sites of inflammation and tumor growth, the local concentration of extracellular adenosine rapidly increases and plays a role in controlling the immune responses of nearby cells. Adenosine deaminases ADA1 and ADA2 (ADAs) decrease the level of adenosine by converting it to inosine, which serves as a negative feedback mechanism. Mutations in the genes encoding ADAs lead to impaired immune function, which suggests a crucial role for ADAs in immune system regulation. It is not clear why humans and other mammals possess two enzymes with adenosine deaminase activity. Here, we found that ADA2 binds to neutrophils, monocytes, NK cells and B cells that do not express CD26, a receptor for ADA1. Moreover, the analysis of CD4+ T-cell subset revealed that ADA2 specifically binds to regulatory T cells expressing CD39 and lacking the receptor for ADA1. Also, it was found that ADA1 binds to CD16- monocytes, while CD16+ monocytes preferably bind ADA2. A study of the blood samples from ADA2-deficient patients showed a dramatic reduction in the number of lymphocyte subsets and an increased concentration of TNF-α in plasma. Our results suggest the existence of a new mechanism, where the activation and survival of immune cells is regulated through the activities of ADA2 or ADA1 anchored to the cell surface.