Evaluation and Management of Deficiency of Adenosine Deaminase 2: An International Consensus Statement.

Importance: Deficiency of adenosine deaminase 2 (DADA2) is a recessively inherited disease characterized by systemic vasculitis, early-onset stroke, bone marrow failure, and/or immunodeficiency affecting both children and adults. DADA2 is among the more common monogenic autoinflammatory diseases, with an estimate of more than 35 000 cases worldwide, but currently, there are no guidelines for diagnostic evaluation or management. Objective: To review the available evidence and develop multidisciplinary consensus statements for the evaluation and management of DADA2. Evidence Review: The DADA2 Consensus Committee developed research questions based on data collected from the International Meetings on DADA2 organized by the DADA2 Foundation in 2016, 2018, and 2020. A comprehensive literature review was performed for articles published prior to 2022. Thirty-two consensus statements were generated using a modified Delphi process, and evidence was graded using the Oxford Center for Evidence-Based Medicine Levels of Evidence. Findings: The DADA2 Consensus Committee, comprising 3 patient representatives and 35 international experts from 18 countries, developed consensus statements for (1) diagnostic testing, (2) screening, (3) clinical and laboratory evaluation, and (4) management of DADA2 based on disease phenotype. Additional consensus statements related to the evaluation and treatment of individuals with DADA2 who are presymptomatic and carriers were generated. Areas with insufficient evidence were identified, and questions for future research were outlined. Conclusions and Relevance: DADA2 is a potentially fatal disease that requires early diagnosis and treatment. By summarizing key evidence and expert opinions, these consensus statements provide a framework to facilitate diagnostic evaluation and management of DADA2.

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.

Adenosine Deaminase Two and Immunoglobulin M Accurately Differentiate Adult Sneddon's Syndrome of Unknown Cause.

BACKGROUND: The association that exists between livedo reticularis (LR) and stroke is known as Sneddon's syndrome (SnS). The disorder is classified as primary SnS (PSnS), if the cause remains unknown and secondary SnS. The condition is rare and it occurs mainly sporadically. In 2014, 2 independent teams described a new genetic disorder with childhood-onset, which was called deficiency of adenosine deaminase 2 (DADA2), characterized by recurrent fevers and vascular pathologic features that included LR and stroke. All the patients carried recessively inherited mutations in cat eye syndrome chromosome region candidate 1 gene (CECR1), encoding the adenosine deaminase 2 (ADA2) protein. Genetic testing is the standard for the diagnosis of DADA2. However, the diagnostic accuracy of more affordable laboratorial analysis in CECR1-mutated individuals remains to be established. We aim to determine whether plasma ADA2 activity and serum immunoglobulin M (IgM) levels can distinguish (1) DADA2 from other adult patients within the SnS spectrum, and (2) healthy CECR1 heterozygous (HHZ) from healthy controls (HC). METHODS: ADA2 activity in plasma and serum IgM concentrations was measured in adult patients within the SnS spectrum, healthy first-degree relatives and HC. Genetic results were used as the reference standard. The primary outcome measures were sensitivity and specificity derived from receiver operating curve analysis. RESULTS: A total of 73 participants were included in the study: 26 patients with PSnS with no CECR1 mutation (PSnS), 6 bi-allelic (DADA2 patients) and 7 HHZ CECR1 mutations and 34 HC. Plasma ADA2 activity and serum IgM levels were significantly lower in DADA2 patients than in PSnS. With the use of the best indexes, plasma ADA2 activity differentiated PSnS from DADA2 with a sensitivity and specificity of 100.0% and HHZ from HC with a sensitivity of 97.1% and specificity of 85.7%. Serum IgM levels also differentiated PSnS from DADA2 with a sensitivity of 85.2% and specificity of 83.3%. CONCLUSION: Serum IgM levels might be used as a triage tool and plasma ADA2 activity performs perfectly as a diagnostic test for DADA2 in adult patients within the SnS spectrum. ADA2 activity in plasma also reliably distinguishes HHZ from HC.