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.

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.

Deficiency of adenosine deaminase 2 as an unrecognized cause of early-onset stroke and cranial nerve palsy

OBJECTIVE

The aim of this study is to evaluate the clinical, laboratory, and radiological findings and prognosis of patients with adenosine deaminase 2 deficiency (DADA2) and to highlight the conditions that DADA2 should be considered in the differential diagnosis in patients with neurological findings.

METHODS

A case series of six DADA2 patients was presented in this retrospective, descriptive study. Clinical and laboratory data, treatment protocols, and prognosis of the patients were recorded. A diagnosis of DADA2 was established by ADA2 enzyme activity assay and/or ADA2 gene sequencing.

RESULTS

Six patients with DADA2 were included in the study. The median age at symptom onset was 6.5 years (range 3.5-13.5 years). The median time to diagnosis from the initial presentation was 9 (3-72) months. Consanguinity was present in the families of 4 cases. The skin, nervous system, and musculoskeletal system were the most commonly involved systems. Vasculitis mimicking polyarteritis nodosa (PAN) was the predominant phenotype (n=4) in our case series. Four patients with PAN-like features had neurological involvement. Ischemic strokes were found in 3 patients, cranial nerve palsy in 2 patients, and seizures in 2 patients. The CECR1 gene was analyzed in all patients. We analyzed plasma ADA2 enzyme activity only in one patient. Anti-tumor necrosis factor (TNF)-α therapy was initiated. Inflammation was suppressed and remission was achieved in all patients.

CONCLUSION

DADA2 should be considered in patients with PAN-like disease, a history of familial PAN/vasculitis, early-onset strokes/neurological involvement with systemic inflammation. Furthermore, anti-TNF-α therapy appears to be beneficial for the treatment of DADA2.

Adenosine Deaminase 2 Deficiency Caused by Biallele Variants Including Splicing Variant: The First Case in Korea

Deficiency of adenosine deaminase 2 (DADA2) is an autoinflammatory disease caused by pathogenic variants of the ADA2 gene and has similar clinical features to polyarteritis nodosa (PAN). We, herein, report a case of DADA2 in Korea that was diagnosed in a patient with childhood-onset PAN. The patient had a truncal ataxia and facial palsy caused by thalamic infarction at 34 months of age. Livedo reticularis with Raynaud phenomenon and abdominal pain with fever were followed. Radiologic examination showed multiple infarctions in brain and kidney. She was diagnosed with PAN using skin biopsy and angiography. She had severe hemorrhagic strokes despite medical treatments. Her disease activity was controlled after adding a tumor necrosis factor-α inhibitor. Molecular analysis revealed compound heterozygous pathogenic variants of ADA2 gene. This is the first case of DADA2 in Korea. Genetic analysis for ADA2 gene should be considered in patients with childhood-onset PAN.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Detailed analysis of Japanese patients with adenosine deaminase 2 deficiency reveals characteristic elevation of type II interferon signature and STAT1 hyperactivation

BACKGROUND

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive inflammatory disease caused by loss-of-function mutations in both alleles of the ADA2 gene. Most patients with DADA2 exhibit systemic vasculopathy consistent with polyarteritis nodosa, but large phenotypic variability has been reported, and the pathogenesis of DADA2 remains unclear.

OBJECTIVES

This study sought to assess the clinical and genetic characteristics of Japanese patients with DADA2 and to gain insight into the pathogenesis of DADA2 by multi-omics analysis.

METHODS

Clinical and genetic data were collected from 8 Japanese patients with DADA2 diagnosed between 2016 and 2019. ADA2 variants in this cohort were functionally analyzed by in vitro overexpression analysis. PBMCs from 4 patients with DADA2 were subjected to transcriptome and proteome analyses. Patient samples were collected before and after introduction of anti- TNF-α therapies. Transcriptome data were compared with those of normal controls and patients with other autoinflammatory diseases.

RESULTS

Five novel ADA2 variants were identified in these 8 patients and were confirmed pathogenic by in vitro analysis. Anti-TNF-α therapy controlled inflammation in all 8 patients. Transcriptome and proteome analyses showed that upregulation of type II interferon signaling was characteristic of DADA2. Network analysis identified STAT1 as a key regulator and a hub molecule in DADA2 pathogenesis, a finding supported by the hyperactivation of STAT1 in patients' monocytes and B cells after IFN-γ stimulation.

CONCLUSIONS

Type II interferon signaling and STAT1 are associated with the pathogenesis of DADA2.

Two siblings presenting with novel ADA2 variants, lymphoproliferation, persistence of large granular lymphocytes, and T-cell perturbations

The presence of large granular lymphocytes has been reported in patients with ADA2 deficiency and T-LGL leukemia. Here we describe two siblings with novel ADA2 variants, expanding the mutational spectrum of ADA2 deficiency. We show that lymphoproliferation, persistence of large granular lymphocytes, T-cell perturbations, and activation of PI3K pathway, measured by means of phosphorylation levels of S6, are detectable in DADA2 patients without T-LGL leukemia.

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.

Deficiency of ADA2 mimicking autoimmune lymphoproliferative syndrome in the absence of livedo reticularis and vasculitis

Adenosine deaminase-2 (ADA2) deficiency (DADA2) is associated with early onset polyarteritis nodosa and vasculopathy. Classic presentation includes livedo reticularis, vasculitis, and stroke. However, the phenotype and disease severity are variable. We present a 5-year-old female who presented with features that mimicked autoimmune lymphoproliferative syndrome (ALPS) in the absence of classic features of DADA2. Exome sequencing identified a novel homozygous splicing variant in ADA2 c.882-2A > G. Patient responded to anti- tumor necrosis factor medication and is in complete remission. Hematologists should be aware of various hematological presentations of DADA2, including ALPS-like disorder, that might lack vasculitis and livedo reticularis to prevent delay in initiating optimal therapy.