Deficiency of adenosine deaminase 2 (DADA2) is a monogenic
autoinflammatory disorder caused by biallelic loss-of-function mutations
in the ADA2 gene (formerly CECR1).
First described in 2014, DADA2 has emerged as a paradigm for monogenic
vasculitis, bridging the gap between primary immunodeficiencies and
systemic vasculitides. The disease is characterized by a remarkably
broad clinical spectrum encompassing early-onset lacunar stroke,
systemic vasculitis resembling polyarteritis nodosa (PAN), hematologic
abnormalities ranging from pure red cell aplasia to pancytopenia,
humoral immunodeficiency, and variable lymphoproliferation. ADA2,
predominantly secreted by myeloid cells, serves dual functions as a
growth factor for endothelial cells and a modulator of extracellular
adenosine metabolism. Its deficiency leads to a proinflammatory state
driven by macrophage dysregulation, excessive tumor necrosis factor
(TNF) production, neutrophil extracellular trap (NET) formation, and
endothelial dysfunction. The genotype–phenotype correlation is complex,
with certain mutations predisposing to vasculitic versus
hematologic-predominant phenotypes. Emerging evidence further links ADA2
deficiency to cellular senescence and inflammaging pathways, suggesting
a connection between monogenic vasculitis and aging-related biological
mechanisms. Anti-TNF therapy has revolutionized disease management,
achieving sustained remission in the majority of vasculitic
manifestations. Hematopoietic stem cell transplantation (HSCT) offers a
definitive cure for severe hematologic disease, while gene therapy
approaches are under active investigation. This review synthesizes
current knowledge on the immunopathogenesis, clinical heterogeneity,
genotype–phenotype correlations, multi-omics insights, and evolving
precision therapeutic strategies for DADA2, positioning it as an
instructive model for understanding monogenic immune vasculopathy.
Despite this progress, fundamental questions remain—including the
relative contribution of ADA2 enzymatic versus growth factor functions
to disease pathogenesis, the mechanisms underlying tissue-specific
vulnerability, the basis of differential treatment responsiveness, and
the identity of genetic and environmental modifiers that determine
phenotypic heterogeneity—that define the frontier of current DADA2
research. This review critically evaluates both established knowledge
and persistent uncertainties, positioning DADA2 as an instructive model
for the study of monogenic immune vasculopathy.