Homozygous Splice ADA2 Gene Mutation Causing ADA-2 Deficiency

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).

Polyarteritis nodosa: an evolving primary systemic vasculitis

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

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

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

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.

Adult-onset deficiency of adenosine deaminase 2-a case report and literature review

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease caused by ADA2 gene mutation that is characterized by three phenotype domains: vasculopathy and inflammation, hematological abnormality, and immunodeficiency. Most patients are pediatric patients; adult-onset patients are only occasionally reported. To describe a Chinese case of adult-onset DADA2 in a Chinese patient and explore the genotype and phenotype characteristics of adult-onset DADA2. We examined the clinical, serological, and genetic features of a Chinese adult-onset DADA2 patient. English literature on DADA2 was reviewed. The clinical and genetic characteristics of different age and mutation subgroups were compared. A Chinese Han male presented with recurrent fever, rash, immunodeficiency, and significant vascular events since the age of 25 years. Serum ADA2 activity was diminished, and genotyping revealed a unique compound heterozygous mutation of exon2-10del/exon7del in the ADA2 gene leading to complete exon 7 deletion. Treatment with a TNFα inhibitor achieved disease control. A total of 269 cases carrying 102 mutations were analyzed through a literature review. Adult-onset patients had few symptoms in all three clinical domains; vasculopathy and inflammation were the major symptoms. Patients with null mutations had early disease onset and more frequent hematological abnormalities and immunodeficiency. Patients in all subgroups responded well to TNFα inhibitors. We reported the first Chinese adult-onset DADA2 patient, with a unique mutation. Screening for and differentiation of DADA2 are recommended for patients of all ages, as they might become symptomatic later in life and treatment strategies differ from those of traditional vasculitis. Key Points • We report a novel compound heterozygous deletion mutations of exons 2-10 and exon 7, leading to complete loss of exon 7 in the ADA2 gene. • Adult-onset DADA2 patients had high similarity to systemic vasculitis. • Null mutations contribute to earlier disease onset and more aggressive disease. • We suggest screening for DADA2 in patients with significant central vasculitis, hematological abnormality and immunodeficiency.

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.

Deficiency of Adenosine Deaminase 2 (DADA2): Hidden Variants, Reduced Penetrance, and Unusual Inheritance

PURPOSE

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disorder that manifests with fever, early-onset vasculitis, strokes, and hematologic dysfunction. This study aimed to identify disease-causing variants by conventional Sanger and whole exome sequencing in two families suspected to have DADA2 and non-confirmatory genotypes. ADA2 enzymatic assay confirmed the clinical diagnosis of DADA2. Molecular diagnosis was important to accurately identify other family members at risk.

METHODS

We used a variety of sequencing technologies, ADA2 enzymatic testing, and molecular methods including qRT-PCR and MLPA.

RESULTS

Exome sequencing identified heterozygosity for the known pathogenic variant ADA2: c.1358A>G, p.Tyr453Cys in a 14-year-old female with a history of ischemic strokes, livedo, and vasculitis. No second pathogenic variant could be identified. ADA2 enzymatic testing in combination with quantitative RT-PCR suggested a loss-of-function allele. Subsequent genome sequencing identified a canonical splice site variant, c.-47+2T>C, within the 5'UTR of ADA2. Two of her unaffected siblings were found to carry the same two pathogenic variants. A homozygous 800-bp duplication comprising exon 7 of ADA2 was identified in a 5-year-old female with features consistent with Diamond-Blackfan anemia (DBA). The duplication was missed by Sanger sequencing of ADA2, chromosomal microarray, and exome sequencing but was detected by MLPA in combination with long-read PCR sequencing. The exon 7 duplication was also identified in her non-symptomatic father and younger sister.

CONCLUSIONS

ADA2 pathogenic variants may not be detected by conventional sequencing and genetic testing and may require the incorporation of additional diagnostic methods. A definitive molecular diagnosis is crucial for all family members to make informed treatment decisions.