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PubMed This is a summary of 23 peer-reviewed journal articles Updated
Rheumatology

Starting Your Journey with DADA2

At a Glance

DADA2 is a very rare inherited condition caused by two non-working copies of the ADA2 gene. It can begin at any age and cause blood vessel inflammation, blood problems, rashes, or fevers, so enzyme activity testing and genetic sequencing can help explain varied symptoms and guide care.

Receiving a diagnosis of Deficiency of Adenosine Deaminase 2 (DADA2) often marks the end of a long and confusing journey. Because DADA2 was only first described in 2014, many patients and families have spent years searching for answers, sometimes receiving several different diagnoses before the true cause was found [1][2]. Understanding this condition begins with recognizing that it is an ultra-rare genetic disease, meaning it affects a very small number of people worldwide [3].

While scientists are still learning exactly how many people have DADA2, some genetic models estimate a population prevalence of approximately 1 in 222,000 people globally, though the number of clinically diagnosed patients is much smaller [3]. Because it is so rare and its symptoms can look like many other diseases, it is frequently underdiagnosed [4].

The “Diagnostic Odyssey”

Many families describe their experience as a “diagnostic odyssey”—a series of appointments, tests, and incorrect labels. Because DADA2 can cause many different symptoms, patients are often initially diagnosed with other conditions, such as:

  • Polyarteritis nodosa (PAN): A form of blood vessel inflammation [5].
  • Behçet disease: A disorder that causes blood vessel inflammation throughout the body [6].
  • Systemic juvenile idiopathic arthritis: A type of childhood arthritis [7].
  • Diamond–Blackfan anemia: A rare genetic blood disorder where the bone marrow fails to make red blood cells [8].

Connecting these seemingly unrelated issues to a single genetic cause is a major turning point in your care.

How DADA2 Happens: Genetics 101

DADA2 is an autosomal recessive disorder. This means that for a person to have the disease, they must inherit two copies of a non-working ADA2 gene (formerly called CECR1)—one from each parent [9][10].

  • Carriers: Parents are usually “carriers.” They have one working gene and one non-working gene. Most carriers do not have DADA2 symptoms [11].
  • Inheritance: When two carriers have a child, there is a 25% chance the child will inherit both non-working genes and have DADA2 [10].

Proposed Biological Mechanisms

Researchers are still clarifying exactly how the loss of the ADA2 enzyme causes the different manifestations. The ADA2 enzyme is a protein produced by certain white blood cells called myeloid cells (like macrophages and monocytes) [12].

Current research models suggest the enzyme has two main roles:

  1. Breaking down adenosine: It is believed to act like a “cleanup crew” to break down a chemical called adenosine outside of cells [13]. A leading hypothesis is that when the enzyme is missing, adenosine builds up, which may trigger harmful inflammation [14].
  2. Supporting blood vessels: It may act as a growth factor, helping to maintain the health and integrity of the endothelium (the thin lining of the blood vessels) [12][15].

When these processes fail, it is proposed that the immune system shifts into an aggressive inflammatory state [16]. This sustained inflammation attacks the walls of the blood vessels. When the lining of a blood vessel is damaged, it can lead to vasculopathy (blood vessel disease), which may cause the vessels to narrow, leak, or clog [17][15]. This mechanism is thought to explain why DADA2 is often associated with skin rashes and a risk of stroke [10].

When Do Symptoms Start?

While DADA2 is often thought of as a childhood disease, it can appear at any age. While some observational cohorts suggest an average onset around 7 to 8 years old, many people are diagnosed in infancy, and others do not show signs until they are well into adulthood [18][19].

The symptoms can also vary based on how much “residual” (leftover) enzyme activity a person has. In population-level studies, patients with almost no enzyme activity often develop blood problems early in life, while those with a small amount of activity might only experience skin rashes or fevers [20][21]. However, genotype or residual enzyme activity does not reliably predict an individual’s exact clinical course.

Regardless of when it starts, a confirmed diagnosis allows your medical team to move away from guesswork and toward a management plan tailored to your specific symptoms [22][23].

Common questions in this guide

What is DADA2, and what parts of the body can it affect?
Deficiency of adenosine deaminase 2, or DADA2, is an ultra-rare inherited condition caused by changes in both copies of the ADA2 gene. It can disrupt inflammation and affect blood vessels, blood cells, and the immune system, so symptoms can differ widely from one person to another.
How is DADA2 passed down in families?
DADA2 is autosomal recessive, which means a person usually must inherit one non-working ADA2 gene copy from each parent. When both parents are carriers, each pregnancy has a 25% chance of resulting in a child with DADA2, and carriers usually do not have symptoms.
Why can it take so long to get a DADA2 diagnosis?
DADA2 is very rare, and its symptoms can resemble conditions such as polyarteritis nodosa, Behçet disease, systemic juvenile idiopathic arthritis, or Diamond–Blackfan anemia. This can lead to multiple appointments and diagnoses before enzyme activity testing and genetic sequencing connect the findings to DADA2.
At what age do DADA2 symptoms usually begin?
DADA2 can begin in infancy, childhood, or adulthood; some studies report an average onset around 7 to 8 years, but that average does not predict an individual’s experience. People with very little ADA2 enzyme activity may develop blood problems earlier, while others may first have rashes or fevers, but enzyme activity and gene changes cannot reliably forecast the full course.
Which tests help confirm DADA2?
Doctors may evaluate ADA2 enzyme activity and perform genetic sequencing of the ADA2 gene. Your team can explain what the exact results mean and how they fit with your symptoms and family history.
Which specialists may be involved in DADA2 care?
Care is often coordinated among specialists based on the person’s symptoms, such as rheumatology for inflammation, hematology for blood problems, and neurology for nervous-system concerns. A genetics professional may also help interpret testing and discuss screening for siblings or other relatives.

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References

References (23)
  1. 1

    A decision tree for the genetic diagnosis of deficiency of adenosine deaminase 2 (DADA2): a French reference centres experience.

    Rama M, Duflos C, Melki I, et al.

    European journal of human genetics : EJHG 2018; (26(7)):960-971 doi:10.1038/s41431-018-0130-6.

    PMID: 29681619
  2. 2

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

    Celikel E, Aydin F, Tekin ZE, et al.

    Northern clinics of Istanbul 2023; (10(4)):411-417 doi:10.14744/nci.2022.45380.

    PMID: 37719263
  3. 3

    Comprehensive analysis of ADA2 genetic variants and estimation of carrier frequency driven by a function-based approach.

    Jee H, Huang Z, Baxter S, et al.

    The Journal of allergy and clinical immunology 2022; (149(1)):379-387 doi:10.1016/j.jaci.2021.04.034.

    PMID: 34004258
  4. 4

    Adenosine deaminase type 2 deficiency: From rare to common.

    Wouters M, Kienapfel V, Ehlers L, et al.

    Journal of human immunity 2026; (2(5)):e20260015 doi:10.70962/jhi.20260015.

    PMID: 42549333
  5. 5

    Identification of Novel Adenosine Deaminase 2 Gene Variants and Varied Clinical Phenotype in Pediatric Vasculitis.

    Gibson KM, Morishita KA, Dancey P, et al.

    Arthritis & rheumatology (Hoboken, N.J.) 2019; (71(10)):1747-1755 doi:10.1002/art.40913.

    PMID: 31008556
  6. 6

    Deficiency of Adenosine Deaminase 2 Masquerading as Behçet's Disease: Phenotypic Mimicry with HLA-B*51 Positivity.

    Almojali A, Alrasheed A, Alharbi B, et al.

    Journal of clinical immunology 2025; (45(1)):83.

    PMID: 40097865
  7. 7

    ADA2 deficiency (DADA2) misdiagnosed as systemic onset juvenile idiopathic arthritis in a child carrying a novel compound heterozygous ADA2 mutation: a case report.

    Yin J, Fan X, Ma J, et al.

    Translational pediatrics 2023; (12(1)):97-103 doi:10.21037/tp-22-261.

    PMID: 36798931
  8. 8

    Infantile Pure Red Cell Aplasia Secondary to Deficiency of Adenosine Deaminase2 (DADA2) Syndrome-Time to Think Beyond Diamond Blackfan Anemia.

    Nayak AR, Dass J, Parikh H, et al.

    Pediatric blood & cancer 2025; (72(6)):e31656 doi:10.1002/pbc.31656.

    PMID: 40095445
  9. 9

    Comparison of disease phenotypes and mechanistic insight on causal variants in patients with DADA2.

    Chen L, Mamutova A, Kozlova A, et al.

    The Journal of allergy and clinical immunology 2023; (152(3)):771-782 doi:10.1016/j.jaci.2023.04.014.

    PMID: 37150360
  10. 10

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

    Lee PY, Davidson BA, Abraham RS, et al.

    JAMA network open 2023; (6(5)):e2315894 doi:10.1001/jamanetworkopen.2023.15894.

    PMID: 37256629
  11. 11

    Dominant negative ADA2 mutations cause ADA2 deficiency in heterozygous carriers.

    Wouters M, Ehlers L, Van Eynde W, et al.

    The Journal of experimental medicine 2025; (222(11)) doi:10.1084/jem.20250499.

    PMID: 40864493
  12. 12

    Pathogenic variant c.1052T>A (p.Leu351Gln) in adenosine deaminase 2 impairs secretion and elevates type I IFN responsive gene expression.

    Bowers SM, Sundqvist M, Dancey P, et al.

    Frontiers in immunology 2022; (13()):995191 doi:10.3389/fimmu.2022.995191.

    PMID: 36248868
  13. 13

    DADA2 as a Model of Monogenic Immune Vasculopathy: From Immunopathogenesis to Precision Therapeutics.

    Peng H, Li C, Mo C, et al.

    Biomolecules 2026; (16(7)) doi:10.3390/biom16071057.

    PMID: 42509849
  14. 14

    Deficiency of adenosine deaminase 2 triggers adenosine-mediated NETosis and TNF production in patients with DADA2.

    Carmona-Rivera C, Khaznadar SS, Shwin KW, et al.

    Blood 2019; (134(4)):395-406 doi:10.1182/blood.2018892752.

    PMID: 31015188
  15. 15

    ADA2 regulates inflammation and hematopoietic stem cell emergence via the A2bR pathway in zebrafish.

    Brix A, Belleri L, Pezzotta A, et al.

    Communications biology 2024; (7(1)):615 doi:10.1038/s42003-024-06286-3.

    PMID: 38777862
  16. 16

    Analysis of deficiency of adenosine deaminase 2 pathogenesis based on single-cell RNA sequencing of monocytes.

    Watanabe N, Gao S, Wu Z, et al.

    Journal of leukocyte biology 2021; (110(3)):409-424 doi:10.1002/JLB.3HI0220-119RR.

    PMID: 33988272
  17. 17

    TNF inhibition in vasculitis management in adenosine deaminase 2 deficiency (DADA2).

    Deuitch NT, Yang D, Lee PY, et al.

    The Journal of allergy and clinical immunology 2022; (149(5)):1812-1816.e6 doi:10.1016/j.jaci.2021.10.030.

    PMID: 34780847
  18. 18

    A wide spectrum of phenotype of deficiency of deaminase 2 (DADA2): a systematic literature review.

    Maccora I, Maniscalco V, Campani S, et al.

    Orphanet journal of rare diseases 2023; (18(1)):117 doi:10.1186/s13023-023-02721-6.

    PMID: 37179309
  19. 19

    DADA2 diagnosed in adulthood versus childhood: A comparative study on 306 patients including a systematic literature review and 12 French cases.

    Fayand A, Chasset F, Boutboul D, et al.

    Seminars in arthritis and rheumatism 2021; (51(6)):1170-1179 doi:10.1016/j.semarthrit.2021.09.001.

    PMID: 34571400
  20. 20

    Genotype and functional correlates of disease phenotype in deficiency of adenosine deaminase 2 (DADA2).

    Lee PY, Kellner ES, Huang Y, et al.

    The Journal of allergy and clinical immunology 2020; (145(6)):1664-1672.e10 doi:10.1016/j.jaci.2019.12.908.

    PMID: 31945408
  21. 21

    Diagnostic Implications and Correlates of Plasma Adenosine Deaminase 2 Activity and ADA2 Variants.

    Yue J, LeSon CE, Rimland CA, et al.

    Arthritis & rheumatology (Hoboken, N.J.) 2026; (78(3)):734-742 doi:10.1002/art.43412.

    PMID: 41147740
  22. 22

    The Many Faces of a Monogenic Autoinflammatory Disease: Adenosine Deaminase 2 Deficiency.

    Kendall JL, Springer JM

    Current rheumatology reports 2020; (22(10)):64 doi:10.1007/s11926-020-00944-1.

    PMID: 32845415
  23. 23

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

    Schnappauf O, Zhou Q, Moura NS, et al.

    Journal of clinical immunology 2020; (40(6)):917-926 doi:10.1007/s10875-020-00817-3.

    PMID: 32638197

This page is for informational purposes only and does not constitute medical advice. Discuss DADA2 testing, family screening, and care planning with your rheumatology, hematology, neurology, or genetics team.

Guide contents Deficiency of adenosine deaminase 2
Research & Literature
02 Symptoms, Warning Signs, and Emergencies in DADA2